The Effect of Anti-Slip Devices on Pedestrian Safety

ISSN: 1402-1544 ISBN 978-91-7439-XXX-X Se i listan och fyll i siffror där kryssen är

DOCTORAL T H E SI S Glenn Berggård Safety Pedestrian Berggårdof on Glenn DevicesEffect Anti-Slip The

Department of Civil, Mining and Environmental Engineering Division of Architecture and Infrastructure

ISSN: 1402-1544 ISBN 978-91-7439-115-2 The Effect of Anti-Slip Devices Luleå University of Technology 2010 on Pedestrian Safety Method Development and Practical Test

Glenn Berggård Method Development and Practical and Development Method Test

The ffect of Anti-lip evices on edestrian afety

Method evelopment and ractical est

Glenn Berggård

Doctoral Thesis 2010

Division of Architecture and Infrastructure Department of Civil, Mining and Environmental Engineering Luleå University of Technology SE-971 87 Luleå Sweden

Printed by Universitetstryckeriet, Luleå 2010

ISSN: 1402-1544 ISBN 978-91-7439-115-2 Luleå 2010 www.ltu.se Preface

The work this thesis is based upon was carried out at the Division of Architecture and Infrastructure, Department of Civil, Mining and Environmental Engineering, Luleå University of Technology.

Financial support from the Swedish National Board for Consumer Policies, the Swedish Rescue Services Agency, the Nordic Council, the COLDTECH foundation and Luleå University of Technology (LTU) is gratefully acknowledged.

I would like to thank my supervisors, Ander Lagerkvist and Charlotta Johansson, at the Department, for their inspiring guidance during the work towards this thesis. Special thanks are due to Charlotta Johansson. I would also like to thank Gunvor Gard, at the Department of Health Care Sciences, Luleå University of Technology, for collaboration and long-term encouragement during most of the research. I am also grateful for the support of Göran Westerström, Head of the Department during the final stages of the work, and to Karin Brundell-Freij, Lars Leden and Per Gårder for valuable comment on earlier drafts of the thesis.

I would like to thank Bert Lindström and Jan Hellström at Väglaboratoriet i Norr AB for their hospitality and kindness in preparing all the test tracks and for taking care of our subjects, and Peter Jäger for carrying out the last Laboratory test.

A big thanks to all the people who volunteered and risked their health, and even their lives, walking on our test tracks without any safety equipment.

Many thanks are also due to staff at FIOH, Carita Aschan and Mikko Hirvonen, for sharing their expertise in fruitful discussions on anti-slip devices and test methods, and collaboration in one of the studies.’

Last, but definitely not least, I thank my wife Nina, for consistently encouraging me.

I thank you all.

Luleå, June 2010

Glenn Berggård (former family name Lundborg)

I List of variables, as defined in this work

Accident = An accident is a specific, identifiable, unexpected, unusual and unintended action that occurs in a particular time and place. It implies a generally negative outcome which may have been avoided or prevented had circumstances leading up to it been recognized, and acted upon. Collision = A collision is an isolated event in which two or more moving bodies (colliding bodies) exert relatively strong forces on each other for a relatively short time. Exposure = A state in which someone is in the traffic environment, either travelling or stationary, which can be quantified in terms of distance travelled, time spent in the environment and/or specific times and places spent in it. Fall = An occurrence due to loss of balance in which a part of the body other than the feet makes contact with the ground. Foot-blade device = An anti-slip device used only under the forefoot. Heel device = A device attached under the heel. Incident = An occurrence of skidding, slipping, stumbling or loss of balance by any other means in which a pedestrian needs to correct or take some action to avoid falling. Injury = Damage or harm to the body, structural or functional, caused by a force or outside agent. Risk = A combination of the likelihood of an occurrence of an event during exposure and the severity of injury that could be caused by the event. Single-pedestrian accident = An accident that occurs to a pedestrian, that may or may not result in injuries, without the involvement of any other road-user. Slip = Relative motion between a shoe or anti-slip device and the road surface on which the pedestrian is moving. Whole-foot device = A device covering more than half of the shoe, or located underneath both the heel and the forefoot.

Abbreviations

COF= Coefficient of friction. MCOF = Measured Coefficient of friction. RCOF = Required Coefficient of friction.

II Summary

Every winter, more than 100,000 pedestrians in the Nordic countries receive medical treatment as a result of falls on slippery surfaces. In addition, the risk of injury reduces interest in outdoor activities during the wintertime. Pedestrians injured in single-pedestrian accidents on icy and snowy surfaces also experience more serious injuries than pedestrians injured on other surfaces. Thus, there is a clear need for measures to reduce single-pedestrian injuries and improve the safety of walking, without curtailing the activity, year round.

A “slip accident” occurs when a person loses his/her balance. An attempt is normally made to recover one’s balance, and the person’s balance is either recovered or a fall occurs. An injury may be the consequence of such a fall. The most critical phases of the human gait are the heel strike and the toe-off.

Various countermeasures can be used .to reduce the risk of a person slipping and sliding when walking outdoors during the wintertime. Such countermeasures may involve the use of individual equipment, services provided by the community to assist vulnerable road-user groups or the public at large, and policy changes in winter-maintenance practices. Examples of measures targeting individuals include information on the risk of slipperiness, and encouraging the use of (or providing) winter footwear and/or anti-slip devices to be fastened to shoes.

The issues considered in this thesis are related to the prevention of injuries from single- pedestrian accidents by a specific measure, the use of anti-slip devices. More specifically, the following questions have been addressed in the studies it is based upon: How can the properties of anti-slip devices be assessed? How can more effective anti-slip devices be developed? Do anti-slip devices improve walking ability and safety?

In laboratory investigations, test methods were developed and applied to 33 anti-slip devices to assess the test methods against validated criteria, and to analyse the benefits of using different types of anti-slip devices. The tests were conducted by observing people making standard movements on various surfaces chosen to simulate the variations in winter maintenance standards on walkways: snow on ice, sand on ice, gravel on ice, salt on ice and pure ice. Movements were analysed from observations of video recordings, and subjective rating scales were developed to assess walking safety and walking balance. In addition, in a field study questionnaires were used to record exposure, occurrence of slips/falls, descriptions of the slips/falls that occurred and general experiences of the use of anti-slip devices.

The results show that it is possible to record the performance of anti-slip devices for pedestrians in a laboratory setting, and that the method developed for doing this is satisfactory. The methods used, together with friction measurements made by the Finnish Institute of Occupational Health (FIOH), may provide a sound basis for establishing standard methodology for testing anti-slip devices as personal protective equipment. The results from the Laboratory tests can be used to identify favourable designs of anti-slip devices, and indicate that whole-foot devices are the best type, followed by heel devices, for supporting a natural gait. The results from the Field study show that the availability and use of anti-slip devices can promote walking, which is beneficial from a health perspective, and it

III does not lead to an increased risk of slipping/falling even though it increases exposure. Overall, the results indicate that the use of anti-slip devices is an effective traffic safety countermeasure for reducing single-pedestrian accidents.

Aspects that warrant further attention include verification of the effects of anti-slip devices on exposure and the occurrence of falls, and their effects in relation to specific groups such as elderly.

Keywords: Fall injuries; Pedestrians; Exposure; Anti-slip devices; Assessment; Test method; Safety; Prevention; Icy surface; Wintertime.

IV Sammanfattning

Säkerhetseffekter av halkskydd för fotgängare – Metodutveckling och praktiska tester

I de Nordiska länderna beräknas mer än 100000 personer uppsöka sjukvård vintertid på grund av fall på snö och is. I Sverige beräknas ca 10000 män och 15000 kvinnor uppsöka sjukvård på grund av skada vid fall på snö och is. Personer skadade i fallolyckor på snö och is har svårare skador och längre konvalescenstid jämfört med fotgängare som faller på barmark. Därför är det viktigt att identifiera preventiva metoder för fallolyckor vintertid och möjliggöra säkra promenader året runt.

En fallolycka inträffar när personen förlorar sin balans och alla försök att återfå den misslyckas. En skada kan uppkomma till följd av ett sådant fall. De kritiska momenten i gångcykeln är hälisättningen och fotavvecklingen (avstampet).

Olika åtgärder kan vidtas för att reducera fallolyckor vintertid. De kan antingen relateras till åtgärder i miljön som snöröjning, halkbekämpning osv, eller vara inriktade på att stödja individen i form av balansträning, information om väderlek med hög halkrisk, skor med bra egenskaper eller halkskydd.

I detta arbete är fokus på att förhindra skador från singelfotgängarolyckor med en individuell åtgärd, halkskydd.

Syftet är att besvara följande forskningsfrågor: Hur kan olika egenskaper hos halkskydd testas? Hur kan effektivare halkskydd utvecklas? Förbättrar halkskydd gångförmågan och säkerheten?

Halkskydd är av principiellt olika typer: helfotsskydd (vilka täcker hela eller huvuddelen av skons undersida), hälskydd (vilka i huvudsak täcker klacken under skon) samt fotbladsskydd (som i huvudsak täcker främre delen av undersidan på skon).

I laboratoriestudier har en testmetodik utvecklats och 33 olika halkskydd har testats. Testbanorna och testcyklerna efterliknar förhållandena i trafikmiljön, speciellt vid anslutning till och på övergångsställen som antas mer fallolycksbelastat. Testerna sker på olika typer av hala ytor för att efterlikna olika driftstandard: grus på is, sand på is, ren is, snö på is samt salt på is. Analys av gångmönster från videoinspelningar har genomförts. Subjektiva metoder har utvecklats för att värdera gångsäkerhet och balans.

I en fältstudie användes enkäter för att registrera exponering, förekomsten av halka och fall, beskrivning av halk- och falltillfällena och generella erfarenheter av användningen av halkskydd.

Resultaten visar att det är möjligt att registrera egenskaper hos halkskydd i laboratoriemiljö och att de använda metoderna ger tillfredsställande resultat. Testmetoderna har utvärderats i samarbete med FIOH (Finnish Institute of Occupational Health) som utför tester av halkskydd för godkännande enligt EU:s certifieringsregler för personlig skyddsutrustning (CE- märkning). Utvärderingen kan ligga till grund för ett förslag till standardiserad testmetodik för halkskydd.

Olika kvaliteter hos halkskydd har kunnat identifieras vid gång på de olika ytorna. Helfotsskydden stödjer bäst en naturlig gång. Hälskydden är näst bäst i att stödja en naturlig gång.

Fältstudien visar att de som använde halkskydd hade signifikant högre exponering utan att få en ökade förekomst av halkincidenter/fall.

Halkskydd kan antas vara en effektiv trafiksäkerhetsåtgärd för att minska fotgängarolyckor

Nya studier rekommenderas för att verifiera effekten av halkskydd på exponering som fotgängare och förekomsten av fallolyckor samt även effekten för olika grupper som t ex äldre.

VI List of Papers

This doctoral thesis is based on the following papers, which are referred to in the text by the corresponding Roman numerals.

I. Gard, G.; Lundborg, G., 2001. Test of Swedish anti-skid devices on five different slippery surfaces. Accident Analysis & Prevention 33, pp. 1-8. II. Gard, G.; Lundborg, G., 2000. Pedestrians on slippery surfaces during winter – methods to describe the problems and practical tests of anti-skid devices. Accident Analysis & Prevention 32, pp. 455-460. III. Berggård, G.; Gard, G., Anti-slip devices – Evaluations of means to prevent pedestrians from falling when walking on slippery surfaces during winter. Submitted to Accident Analysis & Prevention. IV. Lundborg, G., 2001. Anti-slip devices – a need for a standardised test method. CAES, 2001, Hawaii, USA. In Proceedings of the International Conference on Computer-Aided Ergonomics and Safety CAES´2001. CD-ROM, ISBN 84- 931134-7-6. V. Gard, G.; Berggård, G., 2006. Assessment of anti-slip devices from healthy individuals in different ages walking on slippery surfaces. Applied Ergonomics 37, pp. 177–186. VI. Berggård, G.; Gard, G.; Hirvonen, M.; Aschan, C., Criteria for use of anti-slip devices – towards a standardized test method. Submitted to Safety Science. VII. Berggård, G.; Johansson, C., 2010. Pedestrians in wintertime – Effects of using anti-slip devices. Accident Analysis & Prevention 42, pp. 1199-1204.

Impact ratings of the Journals used for publications: Accident Analysis & Prevention, 2008: 1.963 Applied Ergonomics, 2008: 1.250 Journal of Safety Science, 2008: 0.836

Glenn Berggård (former family name Lundborg)

VII VIII Table of contents

Summary ...... III Sammanfattning ...... V List of Papers...... VII 1. Introduction...... 1 1.1 State of the art ...... 2 1.1.1 Pedestrians’ out-door activities during wintertime ...... 2 1.1.2 Single-pedestrian and fall accidents...... 2 1.1.3 Injuries from single-pedestrian accidents during wintertime...... 3 1.1.4 Measures to reduce injuries from single-pedestrian accidents during wintertime .... 4 1.1.5 Effects of anti-slip devices ...... 5 1.1.6 Quality assessment of anti-slip devices...... 6 1.2 Aims and scope of the work...... 7 1.2.1 Demarcation ...... 7

2 Scientific perspective...... 9 2.1 Traffic safety research...... 9 2.2 Slip mechanism and friction...... 9 2.3 Prevention research ...... 12

3 Methods and materials ...... 15 3.1 Order and contents of the tests ...... 15 3.2 Materials and procedures ...... 17

4 Results...... 21 4.1 Development of test methods...... 21 4.2 Pertinent properties of anti-slip devices...... 23 4.3 Walking ability and safety...... 24 4.3.1 Effects of using anti-slip devices ...... 26

5 Discussion and future research ...... 29 5.1 Development of test methods...... 29 5.2 Development of anti-slip devices...... 31 5.3 Walking ability and safety...... 31

6 Conclusions ...... 33 References ...... 35

List of Appendices Appendix 1. Tested anti-slip devices and their properties Appendix 2. Questionnaire Appendix 3. Daily diary Contributions to the papers Papers I – VII

X 1. Introduction The analysis of injuries sustained in pedestrian accidents has to a large extent focused on collision accidents with vehicles. Knowledge about pedestrian risks has therefore also primarily been related to risks associated with motorised vehicles and pedestrians’ exposure to them. Very little is known about the risks associated with pedestrian activities that do not directly involve vehicles. Traffic accident statistics are mainly based on police-reported vehicle accidents and (occasionally) hospital-reported accidents. In many countries there is little or no knowledge about accidents involving only vulnerable road-users, such as single- pedestrian accidents, single-bicycle accidents, and collisions between cyclists and cyclists, cyclists and pedestrians or pedestrians and pedestrians. Police will usually become involved in the aftermath of such crashes if they are serious, e.g. if there are sever injuries or multiple vehicles are involved.. However, in Sweden, traffic environment accident data are now being collaboratively collected by the police, the healthcare authorities and the Swedish National Road Administration using a web-based system called STRADA (Breen et al., 2008). Therefore, in the future better information on single-pedestrian and single-bicycle accidents will be available.

Within the healthcare system, details of accidents related to consumer products including the severity and type of injury, and cause of the accident, have been recorded for several decades by standard procedures, following (until recently) the European Home and Leisure Accident Surveillance System -- EHLASS. EHLASS has now been replaced by the Injury Data Base (IDB) (IDB, 2008), in which data are compiled according to the ICE-CI WHO standard (International Classification of External Causes of Injuries), which is compatible with the ICD-10 classification of injuries (see WHO ICD-10 and WHO ICD-11). From hospital-based statistics it has become obvious that vulnerable road-users, especially pedestrians, are injured much more frequently in the traffic environment than police-reported traffic accident data reveal.

There are diverse sources of information about vulnerable road-users’ accidents, thus there is no uniform, standard format for presenting statistics related to accidents between, and among, vulnerable road-users. Therefore, various terms are used to describe reported incidents, inter alia, pedestrian-only-injuries, non-motor-vehicle pedestrian accidents, single accidents among pedestrians and single-pedestrian accidents. Here, the term single-pedestrian accident will be used to refer to pedestrians’ accidents that do not involve any other road-user.

Hospital-based injury statistics from Sweden clearly show that single-pedestrian accidents on slippery surfaces, i.e. ice and snow, cause high frequencies of injuries. Annually, 25 - 30 000 people (3.2 per 1000 inhabitants) need medical care for treatment of injuries from falling on ice and snow (Nordin, 2003). Similar conditions, with seasonal variations, occur in many other countries, such as Finland, Norway, Canada, USA and Japan. Every winter, more than 100,000 pedestrians in the Nordic countries are expected to receive medical treatment due to slips and falls in winter weather (based on estimates from Nordin, 2003; Kelkka, 1995 and Perälä et al., 2001).

Social, environmental and individual factors all interactively have the potential to initiate series of events that may lead to an accident or injury (Laflamme, 1998). Hence, diverse precautions can be taken to reduce the risks: -primary prevention measures can be used to prevent the occurrence of an accident -secondary prevention measures can be used to reduce the severity of an accident -tertiary prevention measures can be used to reduce the risk of complications of an injury

The frequencies of, and problems associated with, single-pedestrian accidents on slippery (ice and snow covered) surfaces are considered in the following section, and findings of analyses by other authors regarding the nature and efficacy of countermeasures for primary prevention (and possibly secondary prevention) are presented and discussed. Keywords used in the search for relevant literature were: fall accidents; fall injuries, pedestrians; exposure; anti-slip devices; safety; prevention; icy surface and/or wintertime. It should be noted that rigorous analyses of the safety of vulnerable road-users in general, and pedestrians in particular, must include studies of why and how people walk, and how people are affected by different conditions.

1.1 State of the art

1.1.1 Pedestrians’ out-door activities during wintertime The risk of an injury reduces interest in engaging in outdoor activities during the wintertime. Accordingly, a study of five municipalities in Sweden during the winter of 1999/2000 showed that people reduce their outdoor walking during the wintertime (Wretling, 2002). In total, 8% of the population in these municipalities (and a slightly higher portion of males than females) never, or almost never, walk outdoors during the wintertime. As many as 38% stated that they seldom, almost never or never walk outdoors during the winter. Slippery road conditions and snowfalls are the two most common reasons for elderly people (>65 years old) cancelling an outdoor walking trip during the wintertime. When expecting slippery road conditions, 7.7% cancel shopping trips, 9.8% visits to relatives/friends and 12.7% leisure trips. When snow falls, 8.5% cancel visits to relatives/friends, 10.3% shopping trips and 15.1% leisure trips. The long-term effects of injuries from single-pedestrian accidents on snow and ice are quite serious, with 35% of people involved experiencing pain and motion problems and 5-7% of the injured still requiring attention from social services as a consequence a year after the accident. After a fall, 20% state that they go outdoors much less frequently than previously, up to several months after the fall (Öberg et al., 1996).

The reduction in outdoor activity in general, and walking in particular, has several disadvantages since walking outdoors during the wintertime provides exercise, improves accessibility, enhances freedom, is good for the environment, is safer than other modes of travel, and quicker, according to 65, 16, 13, 3, 2 and 1%, respectively of respondents to a survey reported by Wretling (2002). Further, access to outdoor activities improves both physical and mental health (Küller and Küller, 1994). Walking is the most common leisure- time physical activity among U.S. adults (Rafferty et al., 2002). Brisk walking and vigorous exercise are also associated with health improvements, such as substantial (and similar) reductions in the incidence of coronary events among women (Manson et al., 1999). Thus, there is a clear need for measures to reduce single-pedestrian injuries and improve the safety of walking, without curtailing the activity, year round.

1.1.2 Single-pedestrian and fall accidents According to TSU92 – a questionnaire-based, continuously running national survey in Sweden – single-pedestrians accidents accounted for 49% (1,141,962) of the total number of all road transport accidents (2,335,017) in which people aged 1-84 years were hit, fell and/or hurt, during 1998-2000 (Gustafsson and Thulin, 2003). All of these accidents were self- reported and did not necessarily result in a need for medical treatment. The most highly exposed group is 25-44 years of age, but the largest proportion of single-pedestrian accidents

2 occurs in the age group 7-14 years of age, and the proportion of self-reported single- pedestrian accidents exceeds the proportion of exposure for the youngest group, aged between 1 and 14 years. Between 15 and 24 years exposure and accident proportions are very similar, and for people between 25 and 84 years the proportion of exposure exceeds the proportion of self-reported accidents. Younger people are more at risk than other age groups. The data indicate that 346 single-pedestrian accidents (of all types) occur per million person-kilometres (Gustafsson and Thulin, 2003).

In addition, the largest group of all in-hospital patients in Sweden are those injured in falls, 69,000 out of 129,000 (53%) in total in 1993, according to data presented by Folkhälsoinstitutet (1996), and fall-related injuries accounted for 89,000 (56%) visits to hospitals out of a total of 160,000 visits for various kinds of injuries. This type of injury also results in the longest duration of in-patient care, 13.8 days on average compared to the overall mean of 9.9 days, and 42,000 elderly people were admitted as injured in-patients as a result of all kinds of falls, in 1993. The most severe injuries from falls (demanding the longest in- patient care) occurred on snow- and ice-covered surfaces (Folkhälsoinstitutet, 1999).

1.1.3 Injuries from single-pedestrian accidents during wintertime In a study of road surfaces and exposure in three Sweden municipalities in 1994, the rate of injury was found to be 200 per 100,000 inhabitants or 7.2 per 1,000,000 person-kilometres. Of all the people who had single-pedestrian accidents, 17-30% was treated as in-patients. Of all injured pedestrians, 78% considered the condition of the surface to be a significant contributor to the fall, especially in icy and snow-covered road conditions. The days with mixed road conditions, i.e. bare ground mixed with icy and snowy conditions, were six times more dangerous than summer conditions, and the days with only ice and snow conditions were eight times more dangerous. (Öberg et al., 1996). The negative effects of such conditions regarding the safety of single pedestrians, and the length of in-patient days, have also been reported by Berntman (2003) and Larsson (2002).

Table 1. Risks of outdoor falls on slippery surfaces, and numbers of men and women injured in them. Age Male Female Total group Pop. Injured Injured Relative Pop. Injured Injured Relative Injured Injured % number % risk % number % risk number % 0-09 13.5 19 6.0 0.444 12.5 22 4.0 0.320 41 4.7 10-19 11.9 22 7.0 0.588 11.0 30 5.4 0.491 52 6.0 20-29 13.7 20 6.3 0.459 12.9 48 8.7 0.674 68 7.8 30-39 14.4 31 9.8 0.681 13.4 52 9.4 0.701 83 9.6 40-49 14.2 50 15.9 1.120 13.4 58 10.5 0.784 108 12.4 50-59 12.8 44 14.0 1.094 12.2 103 18.6 1.525 147 16.9 60-69 8.8 51 16.2 1.841 9.3 104 18.8 2.022 155 17.8 70-79 7.3 52 16.5 2.260 9.3 100 18.1 1.946 152 17.5 80-89 3.1 26 8.3 2.677 5.2 35 6.3 1.212 61 7.0 90-99 0.3 0 0 - 0.8 2 0.4 0.500 2 0.2 Total 100 315 100 100 554 100 869 100 Relative risks presented by age group and proportions of male and female people in Sweden (based on Pasikowska, 1998 and Statistics Sweden, 2008).

Pedestrians in single-pedestrian accidents on icy and snowy surfaces experience more severe injuries than those injured on other surfaces immediately after the fall, and their injuries generally continue to be more severe a month and six months later. They also have longer

3 hospital stays, longer periods of sick leave, and a higher frequency of in-patient care (32% compared to 11-13%) (Berntman, 2003).

A study of outdoor falls among 460,000 inhabitants in Sweden (5% of the Swedish population), from January-March and October-December 1996, showed 869 injuries caused by slippery surfaces (Pasikowska, 1998). The relative risk was particularly high (>1.5) among males aged 60-89 and females aged 50-79 (See Table 1).

A study of home and leisure accidents among 460,000 inhabitants (Konsumentverket, 2001) in Sweden in 1999 showed that snow and ice were common causes of injuries in falls among middle-aged adults. The number of injuries per 1,000 inhabitants increased from an average of 1.4 for all age groups to 3.2 in the 65-74 years age group (Konsumentverket, 2001). More recent estimates obtained from Swedish EHLASS data for 2003 indicate that there were ca. 1.4 injuries of this kind per 1,000 inhabitants and 4.2 per 1,000 among the 65-74 years age group (Socialstyrelsen, 2005). Similar trends have been found in analyses of hospital-based injury data indicating that 2 per 1,000 inhabitants of Linköping, Göteborg and Umeå (Öberg et al., 1996) were injured in this way during data gathering periods in the 1990s.

In-patient time is longer for elderly pedestrians (>65 years) involved in single-pedestrian accidents on snow/ice than on other surfaces. They account for half of the in-patient time, but only one-third of the injuries (Larsson, 2002). Older women are generally more active than older men, furthermore their bones are more brittle and are injured more easily (Pasikowska, 1998). The number of deaths due to falls is continuing to increase, in contrast to the general decline in numbers of deaths in motor-vehicle traffic accidents. This increase is higher for older females than can be explained simply by the increase in their numbers in the Swedish population (NCO, 2005).

There are similar problems in other countries with icy and snowy winter roads. For instance, the total number of pedestrians requiring an ambulance due to fall-related winter accidents on Hokkaido island, Japan, increased from 120 in 1984 to 503 in 1994 and 831 in 2004 (Takahashi et al., 2007); the largest proportions of injuries occurring in the city of Sapporo, where 111 people were taken to hospital because of slips and falls outdoors in December 1987 (Hara et al., 1991), 248 in December 1992 (Takamiya et al., 1997) and as many as 351 in December 2001 (Shintani et al., 2003b). The severity of the injuries also increases with age. The teenage group accounts for less than 5% and the 60-79 years age group for about 40% of the injured fallers in Sapporo (Hosotani et al., 2007).

1.1.4 Measures to reduce injuries from single-pedestrian accidents during wintertime Injuries from accidents when walking on snow/ice can be greatly reduced by increasing the friction between the foot and surface, which reduces the risk of slipping and sliding (Nilsson, 1986), or by applying other countermeasures related to either the individual or winter maintenance. Examples of winter maintenance measures include providing protective roofs over sidewalks and bus stops, heating ground surfaces where people walk, and making sure there is adequate snow clearance (accompanied by gritting/sanding or salting, and sometimes just gritting/sanding when there is no new snowfall). Examples of measures related to individuals include providing transport services for the elderly, supplying information on the risk of slipperiness, and recommending or providing adequate winter footwear and/or anti-slip devices that can be mounted on shoes (Nilsson, 1986). Other suggestions to reduce accidents that have been made include improving snow and ice removal from pedestrian surfaces

4 (Pasikowska, 1998). In Sweden, the homeowners along a pathway are responsible for some sections of a pathway’s maintenance, and the municipalities are responsible for other sections. Thus, the standard of maintenance, and slipperiness of the surface often varies along pathways (Lindmark and Lundborg, 1987). Better winter road maintenance and marketing of anti-slip devices could be effective preventive investments for reducing numbers of falls (Pasikowska, 1998). Recommendations for road authorities to focus more on pedestrians have also been made by Öberg et al. (1996), including: Concentration on improving winter maintenance of roads used by pedestrians and surfaces they use in bare ground conditions. Provision of more heated surfaces for pedestrians. Improving winter road maintenance for (in order of priority): elderly pedestrians, adult pedestrians, elderly cyclists, adult cyclists.

The cost of winter maintenance for municipalities in Sweden grew by 14.6% between 2000 and 2005 (SKL, 2007). The construction-cost index increased in this period by 11.7%, and the municipal-cost index by 16.5%. However, the local authorities responsible for snow clearing and gritting/sanding are reducing their budgets for these treatments, or at least not allocating more money, and thus reducing the quality or quantity of non-slip surfaces provided.

In many cities in Hokkaido, Japan, falls were most frequent when there was ca. 3-4 cm on the ground, according to data examined by (Takamiya et al., 1997), and most people who fell did so when the temperature was between -2°C to +6°C. Several kinds of slipperiness frequently occur in Sweden, and winter road maintenance alone cannot prevent all accidents (Norrman, 2000), e.g. drivers must be well informed to take necessary safety measures. A model to predict weather and pavement conditions has been developed to inform pedestrians about conditions (Ruotsalainen et al., 2004) and is used by the Finnish Meteorological Institute to provide winter weather information to pedestrians throughout the municipalities in Finland. It is expected that by warning people about slippery conditions, the number of slipping accidents can be reduced and the safety of pedestrians during the winter can be improved (Aschan et al., 2005).

However, there is no conclusive evidence that anti-slip measures, such as snow removal, anti- slip treatment or the use of personal safety equipment like individual anti-slip devices have significant benefits (Öberg et al., 1996; Elvik, 2000), and the results of even single studies may not be straightforward to interpret. For instance, Shintani et al. (2002) found that spreading up to 167 g/m2 gravel enhanced pedestrians’ sense of security more than using anti- slip shoes, although measurements showed that the coefficient of dynamic friction (CODF) was not significantly improved by spreading that amount of gravel.

1.1.5 Effects of anti-slip devices Grönqvist and Hirvonen (1995), Gao (2001), Abeysekera and Gao (2001) and Gao et al. (2003) have all studied the performance of winter footwear on snow/ice surfaces. These studies, and others regarding pedestrian injuries on ice and snow that have considered effects of anti-slip devices to some degree, indicate that such devices can increase friction and reduce slipperiness (Merrild and Bak, 1983; Bruce et al., 1986). Work-related injuries from slips and falls on ice and snow are also known to be major problems in several countries, especially among people with occupations that involve walking outdoors on foot, such as postal delivery workers (Bentley and Haslam, 1996, Bentley and Haslam, 1998 and Haslam and Bentley, 1999), home helpers (Kemmlert and Lundholm, 2001), drivers (getting in and out and during deliveries), as well as teachers, childminders (AFA Insurance, 2006).

5 Another study found a relatively high frequency of falls requiring medical attention among women living in Sapporo, Japan. The anti-skid performance of their shoes and their experiences of anti-slip devices were also recorded. Of 1382 women surveyed, 16.3% had used detachable anti-slip soles, and 38% had shoes with non-slip features, including 16.3% with pins, knobs or abrasive, ceramic surfaces (similar to sandpaper) on the soles (Hara et al., 1997). No evaluation of the performances of the devices is recorded.

However, evidence of an association between the use of anti-slip devices and prevention of slips and falls is slowly growing, for instance from an intervention study conducted in the USA during the winter of 2003/2004 among 101 fall-prone subjects aged 65 and older. The subjects were randomly assigned to wear an anti-slip device or their ordinary winter footwear outdoors. It was concluded that wearing the tested anti-slip device may reduce the risk of outdoor winter falls, and of non-seriously injurious falls among older community-dwelling people with a history of previous falls (McKiernan, 2005).

Of a total of 93 subjects in a study in Finland, 63 female and 30 male, 64 subjects used anti- slip devices and 29 used studded shoes. The subjects (aged 20 - 80 years) were exposed to three falls. Anti-slip devices or studded shoes were used in one of these three cases. They were also exposed to eight “close to” falls, in which anti-slip devices were used in three cases, studded shoes in two cases and ordinary shoes in three cases. No comparison to non-users was made and the exposure was not registered. (Juntunen and Grönqvist, 2005, Juntunen et al., 2005).

As shown above, injuries caused by falls on slippery surfaces are frequent, thus maintenance of pathways alone is insufficient. Information on slippery conditions is also important to avoid slipping under hazardous weather conditions and at hazardous spots. However, the safety is also dependent on the individual pedestrians and their ability, the shoes they wear, anti-slip devices and their interactions with the specific surface, and access to information about slip properties. Using appropriate winter footwear and anti-slip devices on shoes are essential measures to prevent a person from slipping and falling on ice and snow (Grönqvist and Mäkinen, 1997). The hypothesis that use of appropriate anti-slip devices should reduce the frequencies of falls and injuries is one of the hypotheses that were tested in the studies thesis this is based upon, as described below.

1.1.6 Quality assessment of anti-slip devices Anti-slip devices are regarded as personal protective equipment (PPE). The Maastricht Agreement, Article 129a, states that consumer products must not cause damage to persons or property, and the legislation of EU countries has been adapted to conform with this agreement. The law regarding personal protective equipment, such as anti-slip devices, also states that the manufacturer or distributor of each product is responsible for its safety, but no specific standards have been established. Anti-slip devices must meet essential health and safety requirements stipulated in Council Directive 89/686/EEC (Grönqvist and Mäkinen, 1997), which includes provisions regarding the design, construction and manufacture of PPE, including anti-slip devices. Further, tests deemed necessary to show conformity to the basic health and safety requirements of the PPE Directive should be carried out for such products. European standards have been developed to devise practical solutions for harmonizing these essential requirements for various kinds of equipment, but this has not yet been done for anti- slip devices.

6 1.2 Aims and scope of the work The aims of the studies underlying this thesis were to develop knowledge regarding: walking safety for pedestrians during the wintertime, properties of various kinds of anti-slip devices, and their effects on exposure and the risks of slipping and falling. More specific questions addressed included the following:

1. How can relevant properties of anti-slip devices be assessed?

What properties should be evaluated when assessing anti-slip devices? What properties are essential, and what properties can be ignored when comparing different devices? Is there a need for new assessment methods to be developed? Is there a need for a standardised test method?

2. How can more effective anti-slip devices be developed?

Which of today’s anti-slip devises are the best to prevent a person from slipping? What are the best designs of devices? How can existing devices be improved?

3. Do anti-slip devices improve walking ability and safety?

What is the risk exposure among pedestrians with and without anti-slip devices during wintertime? Do anti-slip devices prevent pedestrians from slipping and falling? Do anti-slip devices reduce risks per kilometre walked? What are their effects for the individual? What are their effects for society?

1.2.1 Demarcation This work focuses on pedestrians in the traffic environment. Trips and falls on slippery surfaces outdoors during occupational activities in wintertime and their prevention have not been considered.

7 8 2 Scientific perspective

2.1 Traffic safety research In traffic safety research it is assumed that frequencies of serious conflicts (dangerous situations), involving two or more road users, are related to frequencies of real accidents (Hydén, 1987). Similarly, it is assumed that there are events that almost end up as near accidents (Svensson, 1998). In a safety hierarchy these situations are found at intermediate levels and further down in such a hierarchy we can find “almost almost near-accidents” (see Figure 1). Therefore, it is presumed that by studying the impact of possible countermeasures in the traffic environment on the ratio of near accidents or “almost almost near-accidents” their likely effects on frequencies of real accidents can be estimated (Svensson, 1998). In this thesis and the underlying studies similar assumptions have been made. Those injured in single-pedestrian accidents during wintertime are expected to be a small proportion of people falling on slippery surfaces outdoors during wintertime, and those falling are expected to be a fraction of those slipping. Thus, by studying the processes of slipping and subsequently falling it should be possible to estimate frequencies of injuries from single-pedestrian accidents during wintertime.

Fall with a severe injury

Fall with an injury

Fall with no injury

Slip, near fall

Minor disruptions to walking

Undisrupted walk

Figure 1. Schematic hierarchy of pedestrian incidents while walking during wintertime, from normal walking through incipient danger and dangerous situations to severe injuries (Based on Hauer 1997, Hydén 1987 and Svensson, 1998). 2.2 Slip mechanism and friction Loss of balance is the event common to all falls, and the factor that most often triggers a single-pedestrian accident. Slipping, tripping and other specific accident mechanisms are all precursors of falls. The loss of balance is typically caused by slipping, tripping, stumbling or catching one’s foot on the ground, but single-pedestrian accidents may also result from a collision between a person’s body and another object, fixed or moving, that the pedestrian walks into. When tripping and stumbling, collision with another person might also prevent the subject from recovering his/her balance, thus resulting in a fall (or in some instances have the

9 opposite result, preventing the person from falling). Slipping can sometimes be managed if the slip distance does not exceed the individuals’ capacity to recover, which is age-dependent. Individual factors, such as age and gender, can be risk factors for slips and falls, along with walking ability and walking patterns among both men and women. An attempt is normally made to recover one’s balance, and the person’s balance is either recovered or a fall occurs. An injury may be the consequence of such a fall (Leclercq, 1999).

During wintertime the loss of balance among those injured in single-pedestrian accidents is mostly related to slipping, therefore the relationships between slipping, falling/not falling and in cases when falling occurs, injury/no injury are of interest in a preventive perspective.

At a more detailed level the most critical phases in the human gait are the heel strike and the toe-off (Grönkvist et al., 1989; Strandberg and Lanshammar, 1981). The primary risk factor for slipping accidents, according to Grönqvist (1995), is poor grip and low friction between the footwear (foot) and the underfoot surface (pavement). The heel contact is considered more challenging for maintaining stability and more hazardous from the slipping point of view than the toe-off phase, since forward momentum maintains the body weight on the leading foot causing a forward slide of the foot (Redfern et al., 2001). A gentle heel landing also reduces collision-forces in the shoe/surface interface during weight acceptance, a factor that is important in maximizing friction and slip resistance in water, oil and snow (Grönqvist, 1999).

The upper figure illustrates walking with typical horizontal force (FH) and vertical force (FV) while the graphs show ground reaction components and their ratio, FH/FV, for one step (right foot). Forward and backward indicates the force direction. Critical phases from a slipping point of view are heel contact (peaks 3 and 4) and toe-off (peaks 5 and 6) phases (Grönqvist et al., 1989). Published with permission from the author.

Figure 2. Gait phases in normal level walking.

10 In these phases the risk of slipping is maximal, and balance can therefore be disturbed, especially in these critical movements. A low coefficient of friction (COF) is required for a slip to occur (see Figure 2), and balance is especially likely to be lost and a fall to occur when the friction is too low so the heel starts to slide excessively. The older the person, the shorter the sliding distance before balance is lost. Various countermeasures can be used to reduce risks of a person slipping, one kind being anti-slip devices.

Adaptations of the gait to slipperiness involve attempts to maximize stability through postural changes during early stance and mid-stance (Llewellyn and Nevola, 1992). The body’s centre of mass is moved forward, facilitating a softer heel landing and providing a greater plantar flexion than during a normal contact phase, thus reducing the heel contact angle to the floor. Hence, the shoe/floor contact area appears to increase during heel touchdown. Due to the lower shear forces available in the shoe/floor interface, the ground reaction profiles are altered, minimizing frictional utilization and thus reducing the vertical acceleration and forward velocity of the body (Llewellyn and Nevola, 1992).

COF limit values can be correlated to the normal variability of the human gait, since walking speed, stride length, anthropometric parameters, etc., may greatly affect the friction requirements during motion (Carlsöö, 1968; Andres et al., 1992). Subjective evaluations of friction have been made in some studies with normal winter shoes and these evaluations have been compared to objective measurements (Grönqvist et al., 1989 and Gao 2001), as shown in Tables 2 and 3.

Table 2. Grading system relating the dynamic coefficient of kinetic friction to subjective evaluations (Grönqvist et al., 1989). Class Explanation Coefficient of kinetic friction 1 Very slip-resistant 0.30 2 Slip-resistant 0.20 - 0.29 3 Marginal 0.15 - 0.19 4 Slippery 0.05 - 0.14 5 Very slippery < 0.05

In a test by Gao (2001) the tendency to slip was registered on a scale from 1 to 5, where 1 indicates a very high tendency to slip and 5 a very low tendency to slip as evaluated by the subjects. A significant correlation was found between subjective ratings of the tendency to slip and objective COF measurements (r=-0.900, p=0.037 < 0.05; see Table 3). Similarly studies of the perceptions of 40 healthy industrial workers by Chiou et al. (2000) indicated that their Perceived Sense of Slip was correlated with COF, although they tended to underestimate slipperiness slightly.

Table 3. Subjective ratings of tendency to slip and COF. 1 = Very high and 5 = very low tendency to slip. (Based on Gao, 2001). Pure ice (0 oC) Ice covered Ice covered Ice covered Ice covered with snow with sand with gravel with salt (3-5 mm) (180 g/m2) (150g/m2) (9g/m2) Subjective 1.16 3.18 4.24 3.22 3.41 rating Objective 0.065 0.054 0.280 0.266 0.130 COF (S.D.) 0.003 0.007 0.011 0.023 0.006

11 The coefficient of kinetic friction (MCOF) of anti-slip devices can be measured, and required coefficients of friction (RCOF) can be assessed in laboratory studies with subjects. However, comparative studies of friction measurement devices have shown that few devices are capable of closely simulating the force and motion of the human gait (Grönqvist, 1995). Hansson et al. (1999) developed a method to estimate the probability of slips and falls based on measurements of available and required friction. Slips with recoveries and slips resulting in falls, on ice, were recorded, and categorized using a force plate underneath the ice and a high- speed video camera. The results show that the numbers of slip and fall events increased as the difference between the required (RCOF) and measured coefficients of friction (MCOF) increased when RCOF > MCOF. These types of measurements and analyses could assist in the design of safer environments (Hansson et al., 1999). In addition, floor slipperiness studies by Chang et al. (2004) and Chang et al. (2006) indicate that both objective and subjective measures of slipperiness are important in field studies, that average friction coefficients and subjective perceptions may agree well with each other and that both might be good indicators of slipperiness. Subjective measures, such as perceived safety and perceived balance, can therefore be validly used for assessing risks of slips and falls.

2.3 Research for prevention The Haddon matrix provides a framework for characterizing and analyzing factors affecting injuries, and it has been widely used for several decades to guide research and facilitate the development of interventions to improve various aspects of public health and safety, including traffic safety. The factors defined by the rows in the matrix refer to the interacting factors that contribute to injuring processes. The matrix for injuries from single-pedestrian accidents involving slips and falls during wintertime is presented in Table 4. In this context, the human element incorporates both behavioural and physical components, while the shoe is both the means of transport and the carrier of the measure intended to improve safety, and the road represents the variable external conditions.

Table 4. Anti-slip devices (based on the Haddon matrix; Haddon, 1980). Element Phases Before fall In fall After fall Human (inherent) Information Emergency Medical Training service Education Behaviour (e. g. drinking and walking) Attitudes

Shoe/anti-slip Primary safety Secondary safety Recovery devices Exposure Slipping, sliding, falling Speed Road (external) Local climate Roadside safety Restoration of road Surface condition Obstacle to fall into/on surface (Evenness, friction, …) Anti-slip treatment

A third dimension could also be added to the two dimensional matrix describe above, covering aspects such as effectiveness, cost, stigmatization, and other (Runyan, 1998).

It is evident, based on the Haddon matrix, that the individual, the interaction and the environment all need to be studied in order to describe all of the possible preventive measures that could be applied to prevent falls and injuries in single-pedestrian accidents. Hence, intrinsic, interaction and extrinsic factors all need to be recorded and studied (see Figure 3).

Intrinsic/Inherent factors: Basic characteristics Age Gender

Physiological characteristics Walking ability Exertion Time to take on and off

Perception Perception of walking balance Perception of walking safety Choice of anti-slip devices for own use

Experiences Experiences of falling Experiences of using anti-slip devices

Extrinsic/External factors:

Surface characteristics Ice/snow conditions Anti-slip treatment Temperature Precipitation

Characteristics of anti-slip devices Heel, whole foot, foot blade

Interaction Exposure Steady, slipping, Distance walked, time and speed sliding, falling

Observed movements Heel strike, toe off, moving ability and walking capacity

Figure 3. Intrinsic and extrinsic factors affecting pedestrians’ movements on icy surfaces during wintertime.

13 14 3 Methods and materials

3.1 Order and contents of the tests Tests were conducted on seven different occasions to: develop the test method, test anti-slip devices, assess the test method, and analyse the benefits of using anti-slip devices. The order and content of the tests are shown in Table 5. The number of subjects varied between the tests, as follows. Initially (Test 0), 10 randomly selected subjects, five female and five male, participated in the development of the test method. Both the objective registered performance of the subjects using the tested devices and the subjects’ reaction to the devices showed only minor differences among the subjects. Therefore, the number of subjects in laboratory tests could be reduced without reducing the possibilities to register differences in performance of different anti-slip devices. Four of the subjects that participated in Test 0, two female and two male, participated in the Laboratory tests A, B, C and D using the methods developed in Test 0. After completing these tests, it was found that a device rejected in the tests had been approved in the Conformité Européenne (CE = in accordance with the appropriate EU Directive) approval process. This aroused strong interest in verifying and further developing the method, in order to compare it to the test procedure used by the Notified body (the organization notified by the European Commission to perform tests according to appropriate EU Directives) that performed the CE-approval process. Another objective of the studies at this stage was to determine if there were any differences in performance of the devices when used by subjects of different ages. The test procedure was benchmarked with respect to friction, and the subject’s age and gender for each type of tested device. Therefore Test E was conducted with 107 subjects, 57% female, all adults, with a wide range of ages (22 to 80 years) to ensure that the test methods were valid and reliable, and the results were compared with results from FIOH. The final test (Test F) was an intervention study, in which adults of all ages from 27-67 years were included. In this test, 60% of the subjects were women.

The tests were done using anti-slip devices available in Sweden that were available either on the market or as prototypes directly from the manufacturer. The tested anti-slip devices were manufactured in various countries, including Sweden, Norway, Finland, Germany, the United Kingdom, Italy, Austria, Canada and the United States. Anti-slip devices are also manufactured in other countries, but they have neither been commercially available in Sweden after entrance into the EU — at least not legally available — nor certified according to CE regulations prior to the tests. Therefore, these devices have not been tested.

Table 5. Order and content of the tests and the appended papers in which they were presented. Test Month/ Results Purpose Participants Number Variables Comments Year presented Total Ages of tested in Paper number (year) anti-slip (M/F) devices 0 February I Development of 10 55-80 4 The subject’s perceived walking safety and balance, 1992 test procedures (5/5) analyses from video recordings of walking postures and movements, time to take on and off anti-slip device, perceived advantages and disadvantages for each anti-slip device, and a priority list for personal use according to three criteria – safety, balance and appearance A February II (+ III) Laboratory test 4 60-65 19 The same variables 1993 (Consumer test) (2/2)

B March II (+ III) Laboratory test 4 60-65 8 The same variables Same subjects as 1994 (Consumer test) (2/2) in A. Two devices had been tested before

C March III Laboratory test 4 60-65 6 The same variables Same subjects as 1995 (Consumer test) (2/2) in B. Two and evaluation of devices had been the test method tested before D March III Laboratory test 4 60-65 5 The same variables Same male 1996 (Consumer test) (2/2) subject as in B. and evaluation of One device had the test method been tested before E Nov-Dec V + VI Laboratory test 107 22-80 3 The same variables +Walking time The devices were 2002 Benchmarking of (46/61) also tested at test procedure. FIOH* Comparison with tests at FIOH F Feb-April VII Field study 61 27-67 3 Same type of 2008 Intervention study (34/37) devices as in E *Finnish Institute of Occupational Health

3.2 Materials and procedures There are several types of anti-slip devices covering different parts of the shoe (see Figure 4). An anti-slip device used only under the forefoot is referred to as a Foot-blade device (F). A device attached under the heel is referred to as a Heel device (H). A device covering more than half of the shoe or located both underneath the heel and the forefoot is referred to as a Whole-Foot device (WF). A device with several parts that can be combined for different uses has also been tested in a combination covering both the heel and the forefoot, and is referred to as an F/WF/H device. A list of all types and brands tested (33), divided into the three different types, is available in Appendix 1 (see also Figure 6).

Figure 4. Main types of anti-slip devices.

Anti-slip devices are primarily used when walking outdoors. They can either be removable or firmly attached to the shoe. Those mounted on the shoe can either be always activated or activated and deactivated by the user.

Activate/ Use Deactivate/ Put on Take of

Store/Carry

Figure 5. The phases in using anti-slip devices.

Besides being actually used the anti-slip devices have to be activated/put on and deactivated/taken of before and after a walk. They also have to be stored or carried to be available for use, and sometimes cleaned to remove snow, sand and so on. All these phases are important for the design of an anti-slip device and when a consumer is choosing an anti- slip device for their personal use. The principal design features and (hence) functional group of each of the 33 tested devices are schematically illustrated in Figure 6.

Figure 6. Principal design features of each of the 33 tested anti-slip devices.

Five different surfaces were used in the tests: snow on ice, sand on ice, gravel on ice, salt on ice and pure ice (see Figure 7) (Papers I and II). The walking area was designed to represent conditions in the traffic environment with different surfaces and a slight lateral inclination (<2.5%). The surfaces were chosen to simulate walkways to which a range of winter maintenance measures had been applied. In particular, including snow on ice before pure ice was chosen to see if snow would become attached to the anti-slip devices and reduce their anti-slip effect on the following, pure ice track.

A walking cycle was chosen to simulate general pedestrian behaviour that also accounts for responses at areas close to, and on, pedestrian crosswalks, since Japanese studies indicate that pedestrians might be more exposed to slips and falls (and associated injuries) during wintertime on crosswalks, especially in sharp transitions from sidewalks to ice-covered pedestrian crosswalks and on black-ice-covered pedestrian crosswalks (Shintani et al., 2002 and Shintani et al., 2003a).

The walking cycle for each walking area was divided into six parts to simulate a stressed walking situation on, or close to, a crosswalk:

1. Walk "normally" across the whole area (walking on a sidewalk or on a crosswalk without stress) 2. Turn around (changing direction when approaching a crosswalk) 3. Walk rapidly 4-5 steps (starting to walk on a crosswalk with approaching vehicles) 4. Stop (stopping for approaching vehicles) 5. Walk backwards 4-5 steps (to avoid being hit by approaching vehicles) 6. Walk rapidly across the whole area (stressed by the approach of vehicles)

All tests were performed at temperatures from -2oC to -7oC, slightly lower than those used by Gao (2001), who compared subjective slipperiness and COF using winter shoes. Therefore, COF values in the tests were expected to be higher than those presented by Gao (2001). Below -10oC, the COF on ice typically increases rapidly because there are no longer free water molecules acting as a lubricant.

10 m

Order 1 Gravel on ice

2 Sand on ice

3 Camera Snow on ice

4 Pure ice

5 Salt on ice

Camera

Figure 7. The test tracks used.

A test method was developed, in which all subjects were videotaped from both the side and front/back then their movements were analysed from the video recordings. The analysed movements and the rating scales are presented in Papers I and II. Subjective rating scales were developed to assess walking safety and walking balance. Questionnaires were used to register the ratings and other data (See Appendix 2 for the last version). No specific safety precautions were taken during the experiments. (Helmets were offered but no subject elected to use them).

In the field study, presented in Paper VII, daily diaries (See Appendix 3) and questionnaires were used to register the background of the subject, exposure, occurrence of slips/falls, description of the slip/fall that occurred and experiences of the use of anti-slip devices. The results were analysed using SPSS 15.0.1. The subjects were chosen from employees of five departments at Luleå University of Technology in Sweden. The subjects were divided into three groups: an Intervention Group (N=25), a Control Group (N=25), with similar distribution of gender and age, and a Comparison Group (N=17). The Intervention Group and the Control Group were invited to participate in a health promotion project and to separate information meetings to discuss problems and benefits of walking during the wintertime and the importance of the study presented here. The Comparison Group was merely informed, in writing, about the importance of their participation in a travel survey. The subjects in the different groups had similar distributions with respect to gender (60% female) and age (27 – 67 years).

4 Results

4.1 Development of test methods The order and content of the tests and the appended papers in which results are presented are listed above in Table 2. In total six tests (O, A-E) were conducted.

The development of a test method is presented in Paper I. Ten subjects and four different types of anti-slip devices were used. The subjects were randomly selected from all residents aged 55 years or more in the city of Luleå in northern Sweden. The four anti-slip devices chosen represent three different designs of anti-slip devices available on the Swedish market: heel, foot blade and whole-foot.

The results from the ratings for perceived walking safety and walking balance were expressed as numbers of subjects with no, bad, fairly good, or good perception for each of the devices on each of the different surfaces. The inter-reliability of the walking safety and balance scales were measured as the percentage of agreement between two physical therapists when observing video-recordings of all subjects in test 0. The ratings for tested reliability of perceived walking safety and walking balance were 86 and 88%, respectively.

The four rating scales for walking movements were also tested for inter-rater reliability by two experienced physiotherapists. The dimensions evaluated were:

Walking posture and movements including normal muscle function in the hip and knee. The two therapists had a rating agreement of 85% Walking posture and movements in the rest of the body (head, shoulders, and arms), 80% agreement Heel strike, 86% agreement Toe off, 85% agreement.

It is important to have as high inter-rater reliability as possible. According to Nunnally (1978), the minimum threshold for satisfactory inter-rater reliability is 70%, which was obviously surpassed in these studies.

The results from Laboratory tests A and B with four subjects (two female and two male) and 25 different anti-slip devices are presented in Paper II. The results from these tests showed that the rating scales describing perceived safety and balance, and the methods for observing movements, were reliable and could be used to describe walking safety, walking balance and walking movements when walking with anti-slip devices on slippery surfaces. The criteria applied to rank anti-slip devices for personal use and list their perceived advantages and disadvantages could also be used in the test situation. These practical criteria are important, since they provide indications of ways to improve the usability of anti-slip devices. The subjective rankings of anti-slip device for personal use by the subjects, according to perceived safety, balance and appearance are also relevant, since people’s own priorities strongly influence their everyday behaviour. Therefore, evaluations of perceived advantages and disadvantages of anti-slip devices after subjects have walked with them should be included in standard tests. Consideration of the subjects’ priorities for anti-slip devices would be a valuable practical measure in future product development, since there is no point in making any product, however objectively good it may be, if no customers choose to buy and use it.

Detailed findings regarding the methods used in all the Laboratory tests are discussed in Paper III, notably that surfaces covered with gravel and sand can be excluded from such tests since they provide too much friction to induce sufficient changes in gait to yield observable differences in the performance of the anti slip devices.

The findings from Tests A-D show that several of the 33 tested devices are non-functional. However, one of them was subsequently CE-approved. Therefore, there is a need for a standardized test to reject anti-slip devices that do not perform adequately. Several other tested devices that did not perform well in the tests have not been CE-approved and are therefore not available on the market.

In Paper IV the findings from the Laboratory tests are compared with indications from other studies. Since 1997 (Grönqvist & Mäkinen, 1997), there have been suggestions for the establishment of a European standard for special footwear and attachments with spikes or studs for occupational use. This is not sufficient. A standard should also be established for special footwear and attachments with spikes or studs for private use, because most injuries from slips and falls occur outside working hours. Therefore, possible methods for use in standard tests were evaluated and compared. The results suggest that measurements of available friction are insufficient for assessing the safety any given device, since human behaviour is also important. Thus, any standard test should have a human-centred approach.

In Paper V the results from a larger laboratory test, Test E, on the use of anti-slip devices by a larger group are presented and the methods used are evaluated. Since the previous laboratory tests (O, A-D) were conducted with a relatively small number of elderly subjects, Test E was conducted to establish better knowledge of whether there were any age- or gender-based differences in the use of the best of each of three types of anti-slip devices (heel, foot blade and whole foot devices) previously identified. A total of 107 subjects participated, aged 22 to 80 years. The time subjects spent walking the set distances with each device was also measured in test E. The results are presented as frequencies of the subjects’ perceptions and observers’ observations in pre-defined classes. For all subjects in Test E, both the objective and subjective methods were useful for comparing the properties of the anti-slip devices, and show that there were significant age- and gender-related differences between the users.

The main issues addressed in Paper VI are the criteria that are important for choosing anti-slip devices and the methods that should be recommended for a European standard for testing anti-slip devices. Most of the subjective and objective methods used in this study were practical, functional and user-friendly, and could be incorporated in a European standard, but video recordings of the walking cycle should probably not be included in a CE-type approval process due to their high costs. Further analysis, conducted by an experienced physiotherapist, based on the video recordings, did not recognise as large differences in walking ability as the subjects’ reports of perceived balance and safety. The reported perceived balance and safety therefore seems to be a more sensitive instrument to register differences in properties of different anti-slip devices.

The movement analysis in its present form could therefore probably be excluded as one of the used methods. However, ideally more convenient movement analysis methods should be developed, for use in objective analyses of similarities and differences in changes in gait induced by the use of anti-slip devices on different surfaces. The focus should be on the feet during the walking cycle, particularly on heel strike and toe off, since they are the most relevant phases in slips and falls.

4.2 Pertinent properties of anti-slip devices The abovementioned methods were used to identify pertinent properties of anti-slip devices, and the results were then used for ranking anti-slip devices.

In Test 0, presented in Paper I, the anti-slip device H2 (a fixed-heel device) performed best in terms of walking safety and balance, choice for personal use and time to take on (activate) and ease of use.

The results from Tests A and B (Paper II) show that the whole-foot device W1, a Wellington boot with the sole covered with studs, was perceived as the best according to walking safety and walking balance, and had the highest overall ranking for personal use. This combination gave a very stable and comfortable walk, and it did not have any parts that could come loose when walking. However, it was not compared in the following tests with new devices since it was a fixed device. Instead, high-ranking detachable devices, such as H7 and W10, were used for comparisons.

Results of tests of eight new devices, Tests C and D, are presented in Paper III. The anti-slip devices were divided into three functional groups: heel devices, whole-foot devices, and foot- blade devices. The devices were detachable or fixed, with the fixed being activated or deactivated. The functional group that provided the best support for a natural gait was the whole-foot device. Results from the four tests, A-D, indicate that only two whole-foot devices, W10 and W11, and one foot-blade device, F2, promoted normal walking capacity, heel strike, toe off, and movement patterns in the rest of the body for all subjects on all surfaces. Whole-foot devices W7, W10, and W11, provided good or very good perceived walking safety and balance on all surfaces. When the subjects chose equipment for their own personal usage, they typically favoured a whole-foot device, such as W11. It is therefore recommended that consumers with no prior experience choose a whole-foot device, for instance W11, to allow a normal gait and to obtain good perceived walking safety and balance on all surfaces.

The results from Test E are presented in Papers V and VI. Three different types of anti-slip devices on the market should theoretically support different phases in normal gait: a heel- device for safe heel strike, a foot-blade device for safe toe off and a whole-foot device for both phases. The selection of tested devices in test E was based on earlier tests (0 and A-D) identifying good examples of anti-slip devices in each of the design groups.

No significant differences were found in the observations of the different anti-slip devices on the different surfaces related to the subjects’ gender or ages. Most subjects walked with normal muscle function in the hip and knee when walking with or without an anti-slip device on all surfaces. The heel device was observed to be the quickest to take on and the toe device the quickest to take off.

However, significantly more women than men perceived the heel device to significantly improve the safety of walking on gravel and ice, and the toe device to significantly improve the safety of walking on sand, gravel, ice and salt. It also took significantly longer for women compared to men to walk on gravel and sand (p<0.05, T-test for two independent samples). Similarly, in the age-related comparisons, significantly more people older than 40 years than younger people perceived the heel device to be the best device for walking on gravel and ice, and the toe device to be the best for walking on sand, gravel, ice and salt (p<0.05, T-tests for two independent samples).

All three devices were perceived to provide a good foothold. The heel device was perceived to fit the shoe and to be stable at heel strike. The toe device was easily portable and stable on uncovered ice. The whole-foot device was comfortable to walk with and safe on snow- covered ice although it did not fit so well on most of the subjects own footwear used in the study. The heel device had the highest ranking with respect to walking safety, walking balance on uncovered ice and on snow-covered ice, and choice for personal use, followed by the toe device and the whole-foot device.

However, a change in movement pattern with the heel device was observed, with a clear heel strike, but a more insecure and unbalanced toe off. Nevertheless, most subjects walked with a normal muscle function in the hip and knee as well as with normal movements in the rest of the body when walking with or without each of the anti-slip devices on all surfaces. The toe device was perceived to be stable on ice, but it did not fit all types of shoes and the spikes could be felt under the foot. The whole-foot device was perceived as good on snow, but some subjects perceived it to be clumsy and ugly and that it moved under the foot, thus reducing the perceived balance.

Paper VI presents results from the laboratory measurements at FIOH done in Test E, showing that the heel device had the highest dynamic coefficient of friction (DCOF) followed by the foot-blade device, in accordance with the perceived results presented above. This may at least partially explain the results, since the heel device was considered the best in terms of walking safety and balance in the last laboratory test.

Figure 8. Location of the studs/points on two types of heel devices (left). To the right a more favourable location along the perimeter.

Findings from the tests of all the anti-slip devices indicate that it is important to locate the studs or pins on the perimeter of the devices (See Figure 8). The anti-slip devices that were ranked most highly had wider spreads of studs or pins, located closer to the perimeter, than lower-ranked devices. This applies to all types of devices: heel devices, foot-blade devices and whole-foot devices.

4.3 Walking ability and safety An intervention study was performed during February to April 2008, and the results are presented in Paper VII. The study focused on 67 healthy adults (40 females and 27 males, divided into an Intervention Group, a Control Group and a Comparison Group) in northern Sweden, to study the effects of using anti-slip devices on daily walking distances and prevention of slips and falls.

A third (35%) of the subjects stated that they reduce their walking distances when surfaces are slippery and 23% that they reduce their walking during snowfalls. In addition, 23% stated that they never used anti-slip devices and 27% that they seldom used anti-slip devices prior to this study. Nearly a third of the females had prior experiences of using anti-slip devices, and stated that they mostly, or always, use such devices. The importance of using anti-slip devices was seen as strong especially among the subjects in the Intervention Group, 44% of whom stated that anti-slip devices are very important. In the Control and Comparison Groups the corresponding percentages were 25% and 29%, respectively. Five subjects stated that they always use anti-slip devices.

There were no significant differences between the groups with respect to mean daily total walking distance and mean daily total walking time. The mean daily total walking distance of the subjects in this study was also similar to the average walking distance according to the Swedish National Travel Survey that is 2-3 km (SIKA Statistics, 2007).

For the subjects using anti-slip devices, the mean daily total walking distance was significantly longer during days when they were using anti-slip devices, than that of people not using anti-slip devices (4.08 versus 2.66 km; df=1, F=86,139, p<0.05). There were also significant differences between younger and older subjects in both total walking distance (df=1, F= 43.277, p = 0.000 <0.05) and the distance walked with anti-slip devices (df=1, F=44.818, p= 0.000 <0.05). The elderly walked longer distances and used anti-slip devices more frequently.

In total, 52% of the respondents used anti-slip devices on at least one occasion in this study. A larger portion, 86%, of the respondents in the Intervention group (all of whom we equipped with anti-slip devices) used anti-slip devices than in the Control and Comparison groups (36 and 31%, respectively). The respondents in the Control and Comparison groups used anti-slip devices of their own. Information about the risks of slipping and falling provided to the Control group did not lead to higher use of anti-slip devices than in the Comparison group, and thus does not seem to promote their use. However, access to anti-slip devices did increase their use.

It should be noted that 55 of 64 incidents/slips reported by the subjects during the study period occurred when they were not using anti-slip devices and only nine when they were using anti-slip devices. Furthermore, six actual falls occurred when subjects were not using anti-slip devices, but only one when a subject was using an anti-slip device, a heel device. There were no significant differences in the frequencies of incidents or falls per walking day between those who used anti-slip devices, 0.025, and those who did not, 0.026. Hence, an increased mean daily total walking distance, associated with using anti-slip devices, did not increase the number of incidents or falls. There were no significant differences between age groups in incidents or fall occurrences; with 33 of the incidences or falls occurring among the younger subjects (44 years) and 31 among the older subjects (45 years).

Users of anti-slip devices experienced 6.2 incidents per 1000 km of walking, while non-users experienced 9.8 incidents per 1000 km of walking. The incidence rate ratio is 0.63, suggesting a protective effect of the anti-slip devices. However, the difference is not statistically significant (t=1.47 according to a t-test based on Poisson assumptions), since the 95 % confidence intervals of incident frequencies for users and non-users are 6.2+/-4.1 and 9.8 +/- 2.6, respectively.

Similarly, the rate of falls was 0.69 per 1000 km of walking for users of anti-slip devices and 1.07 per 1000 km of walking for non-users. The incident rate ratio is 0.64, again suggesting a protective effect of the anti-slip devices. However, this difference is also not statistically significant (t=0.46 according to a t-test based on Poisson assumptions) since the 95 % confidence intervals of fall frequencies for users and non-users are 0.69+/- 0.45 and 1.07 +/- 0.31, respectively. It should be noted that both incidents and falls were events that did not result in personal injury.

The prevalence of all kinds of single-pedestrian injuries, year-round, is 0.345 per 1000 km in Sweden, according to Gustafsson and Thulin (2003). Slip and fall accidents on snow and ice are probably the largest contributors. A comparison of this estimated national rate and rates of incidents recorded in the intervention suggest study shows that the rate of falls rate is 1.8 higher than the risk for a single-pedestrian injury when using an anti-slip device, and 2.8 times higher when not using one.

4.3.1 Effects of using anti-slip devices Eighteen subjects in the intervention study provided information about their experiences of using anti-slip devices over a longer period, fourteen of whom were female, and all of these subjects stated that they would continue to use anti-slip devices and recommend their friends to do so.

The benefits of using anti-slip devices outweigh the disadvantages, because those using appropriate anti-slip devices were found to walk long distances daily, on average, than those who did not use anti-slip devices, without increasing the risk of slips/falls. The study also shows that if people use appropriate anti-slip devices and are provided with information about when and where to use them the number of slips and falls will be reduced.

The Swedish Gross National Product in the year 1998 was 2,012,091 million Swedish crowns (MSEK) (SCB, 2007). The expenditure for all public physical maintenance and construction in Sweden in 1998 accounted for 1.6% of this, or 33,515 MSEK. Most of those investments (24,560 MSEK, 73%) were targeted to the transport sector. Another 1,520 MSEK (4%) was used in residential areas, 1,900 MSEK (6%) in industrial areas, 1,095 MSEK (3%) in schoolyards and areas of other institution, 1,110 MSEK (4%) in sports grounds and 3,330 MSEK (10%) in leisure areas. These costs included maintenance and investments in new construction and reconstruction of existing infrastructure (Räddningsverket, 2002).

In Umeå (pop. 118,544), approximately 3.5 injuries from single-pedestrian accidents per 1,000 inhabitants occurred during one winter season, according to data examined by Björnstig et al. (1997). Fractures occurred in half of the accidents, and in two-thirds of the accidents befalling women >50 years of age. The costs incurred amounted 1993 to 6.2 MSEK for emergency care and sickness benefits, on average 15,000 SEK per injured person. This was approximately the same as the cost for all other types of traffic-related injuries in the same area during the same period. Therefore, injury prevention measures for single pedestrian- related injuries would be as important, from both medical and social perspectives, as injury prevention measures for vehicle-related injuries (Björnstig et al., 1997).

The results presented in Paper VII imply that risks of falls could potentially be reduced by a third by using anti slip devices. Further, reducing the number of people involved in single- pedestrian accidents needing medical treatment by one third (or approximately 10,000 injuries) annually in Sweden should deliver significant savings in expenditures for medical

treatment and healthcare. Based on the abovementioned average costs (1993 expenses corrected for a more than 35% increase in healthcare costs during the period 1993 to 2003; IHE, 2006), more than 10 000 * 20 000 = 200 MSEK could be saved annually in Sweden. The cost of a pair of anti-slip devices is on average approximately 200 SEK. Supplying all of the citizens (9 million) in Sweden with an anti-slip device would cost 1800 MSEK, compared to annual costs of 24,560 MSEK for maintenance and construction of the transport infrastructure, hence anti-slip devices would be a cost efficient measure for reducing injuries in the transport sector.

5 Discussion and future research

5.1 Development of test methods Over a period of several years, 33 different types of anti-slip devices have been tested using both objective and subjective evaluation methods. As previously pointed out, one anti-slip device that was later approved according to the relevant EU Directive did not perform satisfactorily in these tests. This implies a need to develop European and global standards for testing special footwear and attachments with spikes or studs for private use (Papers IV and VI). Comparative tests are required to identify the most appropriate methods, which should include a number of human-centred methodologies, i.e. subjective, objective, and combined approaches, for evaluating slipperiness. They should also include a variety of approaches (biomechanical-oriented analyses, psychophysical tests and subjective evaluations) to evaluate slip resistance properties of footwear, anti-slip devices and floor surfaces in practical tests, as described by Grönqvist et al. (2001). Critical phases in the natural gait on slippery surfaces, such as heel strike and toe off, and the effects of candidate devices on these phases should also be considered to facilitate attempts to determine optimal types of anti-slip device (heel, foot blade or whole foot) for different surfaces.

There are two basic foot movements during the gait, dorsiflexion and plantarflexion, in which the ankle joint acts as a fulcrum. Therefore, the closer the centre of gravity (COGF) of the footwear and the attached anti-slip device are situated, the easier it is to walk. Thus, the COGA (centre of gravity of the anti-slip device) of both tested anti-slip devices and the footwear subjects’ use in the tests should be measured (see Figure 9.)

COG A

COG F Figure 9. Locations of centres of gravity of footwear (COGF) and an anti-slip device (COGA).

The results from a recent study using heel-mounted accelerometers show a reasonably strong relationship between the time taken for the foot to initially decelerate to zero and the magnitude of forward slippage of the heel following heel strike (McGorry et al., 2007). This relationship may provide additional information about slip distance, and may have utility as an adjunct measure, in support of more traditional measures of slipperiness. Future research on the use of heel-mounted accelerometers for recording heel strike and toe off is recommended (Paper VI). In addition, walking restrictions normally increase tension, and might increase the likelihood of slips and falls, thus future research should also include analyses of correlations among frequencies of slips/falls, perceived exertion and both perceived and measured heart rate and muscle tension.

The tracks and walking sequences used in the tests were intended to include conditions mirroring situations where traffic accidents are likely to occur and it may be important to walk

quite quickly, for example at a pedestrian crosswalk, or close to it. The surfaces were also varied, partly because surfaces may vary along a sidewalk from open through snowy to icy, depending on whether the house owner applies anti-slip treatment using sand, gravel or salt, or no treatment. The surface on a pedestrian crosswalk may also vary, depending on the maintenance method used. Walking 10 metres at normal pace, turning, walking a few steps, stopping, walking backwards and then rapidly walking another 10 metres forward are similar to known sequences of actions taken by pedestrians close to or on pedestrian crosswalks. However, future studies should be made to more precisely identify other “black spots” and to provide information about where special precautions should be taken when walking outdoors during the wintertime. Test tracks should also be developed with different inclinations, lateral and in the walking direction, to resemble different kinds of traffic environment, as also described by Shintani et al. (2002). A proposed standard should also involve walking on surfaces other than smooth ice, such as rough surfaces, and surfaces composed of hard, packed snow.

No specific safety precautions were taken during the experiments. Hence the walking pace in the ‘walking rapidly phase’, may have been slower than if safety precautions had been arranged. Further studies should examine the potential importance of safety precautions, such as the influence of using/not using helmets or other safety equipment.

The walking speeds of different age groups on different surfaces should also be considered, since pedestrians are not a homogenous group when using pedestrian crossings (Knoblauch, 1996; Fitzpatrick et al., 2006; Montufar, 2007; Coffin and Morrall, 1995; Langlois et al., 1997). Walking speed and general attention also differ when performing other tasks, such as walking and talking on a cell phone (Hurt and Kram, 2006). Therefore, the effects of walking while performing other tasks on the incidence of slips and falls, and the performance of anti- slip devices, should also be considered.

The step length and walking cycle time appear to be important factors in the attainment of dynamic stability in motion (Grönqvist et al., 2001). Hence in a European standard method for assessing anti-slip devices, these variables should be recorded and compared between anti-slip devices and surfaces.

The proposed method includes measuring the subjects’ attitudes to each anti-slip device and the devices’ properties in terms of design and ease of handling and use both when attached/in use and when carried or stored away, etc. (Berggård, 2008). Any hindrance to mobility of the foot, the weight of the device, and compatibility with other leg protectors and safety footwear should also be assessed.

The coefficient of kinetic friction (MCOF) of anti-slip devices should be measured, and required coefficients of friction (RCOF) should be assessed, based on a study performed with subjects, since results (Hansson et al., 1999) show that the numbers of slip and fall events increased as the difference between the required (RCOF) and measured coefficients of friction (MCOF) increased when RCOF > MCOF. The test method should also be validated using walking tests with different anti-slip devices on different icy surfaces. The devices should be described according to the subjects' perceptions of walking safety, walking balance, and the personal reasons for choosing an anti-slip device for personal use (see Papers I and II).

5.2 Development of anti-slip devices The results from the tests can be used to identify favourable designs, materials and assembly methods for anti-slip devices. The long-term wear and tear of different parts of the anti-slip devices should also be evaluated.

When walking on slippery surfaces, a modified gait is generally used. The step length is decreased, the swing of the leg is restricted and the rollover phase is excluded and replaced by a flat approach by the foot to the ground followed by a flat lift of the foot from the ground. The heel device supports a natural heel strike, the foot-blade device supports a natural toe off, and the whole-foot device supports a natural gait with heel strike, rollover and toe off. The user adapts his/her gait to the specific benefit provided by a specific anti-slip device. Between-gender differences in gait adaptations, and choices of anti-slip devices, may be influenced by women’s much greater experience of walking in high-heel shoes (and thus in use of the foot blade for safe walking).

The best foot-blade devices should provide better support during toe off than the best whole- foot devices, while the best heel devices should provide better support during heel strike than the best whole foot devices. Would an even better whole-foot device perhaps comprise a combination of features of the best foot-blade device and the best heel device? To develop such attractive devices, the advantages of the best devices in each functional group should be considered and incorporated in the development of new anti-slip devices. Since the heel strike is the most important part of the gait for preventing slips and falls, the development of attractive and well-functioning heel devices and whole-foot devices are of great importance for preventing slips and falls.

Essentially, there is a need for better and more convenient whole-foot devices that are light, flexible and permit a normal gait. Devices that are too stiff lead to an unnatural gait with a flat approach of the shoe to the ground, and no normal heel strike or toe off. However, users sometimes seem to consider other aspects. Mainly, they prefer devices that are easy to carry and easy to put on and take off, as noted by Hara et al. (1997) and Haslam and Bentley (1999).

An anti-slip device is expected to help prevent slipping and falling when used properly, according to its functional class (heel, foot blade, or whole-foot). If the anti-slip functionality is built into the shoe, further development should include efforts to make it easier to activate and de-activate the function. Devices that have been built into shoes and can be activated/deactivated could also perhaps be thermostat- or remotely controlled.

5.3 Walking ability and safety The intervention study indicates that use of anti-slip devices can promote increases in daily walking lengths on snowy and icy surfaces, thereby increasing people’s physical strength and health, without increasing (or even reducing) rates of slips and falls. The subjects’ experiences of using anti-slip devices will continue to grow, as will the number of people who recommend others to try such devices. Therefore, further studies on the use of, and effects of using, anti- slip devices are recommended. This will enable us to compare reductions of risks obtained from providing and advocating the use of anti-slip devices with other risk-reduction measures.

Currently, non-vehicle related traffic data are insufficiently detailed to calculate risks of slips, falls and injuries in relation to variables such as the time of day, time of year and type of road surface (Brüde and Wiklund, 2008). Thus, there is a clear need for a standardised procedure to

register the exposure of pedestrians in order inter alia to compare risks of single-pedestrian accidents and vehicle-related accidents. Incidents affecting pedestrians need to be recorded, regardless of whether they occur during part of a trip chain (with other modes of transport) or a specific pedestrian trip, and their rates need to be compared with (for instance) actual, self- reported, observed, or health care system-based injury data to develop a better understanding of the systematic relationships between slips, falls, injuries and exposure, as illustrated in Figure 1.

Anti-slip devices are measures that are primarily intended to reduce the risks of individuals slipping, falling and injuring themselves, although the data acquired in the intervention data do not demonstrate that the tested devices provided significant benefits in these respects. However, they are also health-promoting tools, since the individuals walked further when using anti-slip devices than non-users. Therefore, the effects of using anti-slip devices should be analysed, in more detailed intervention studies, on fall prevention, injury severity reduction, and health-promotion in different groups such as: Occupational groups, e.g. home helpers, nursery school teachers, and other groups who work outside Healthy adults Disabled adults Healthy elderly (65 years of age and older).

In the transport sector, money designated for improving safety is primarily spent on prevention of accidents involving cars and collisions between cars and vulnerable road users. Measures to reduce injuries from single-pedestrians accidents have traditionally been given a low priority. Measures, such as anti-slip devices, to help prevent injuries caused by slipping on icy/snowy surfaces should therefore be given greater priority in the future. The studies this thesis is based upon indicate that anti-slip devices are cost efficient measures for reducing injuries in the transport sector, but their effects (and costs) should be compared in more detail to those of other traffic safety measures in the transport sector.

6 Conclusions The studies show that it is possible to record the performance of anti-slip devices for pedestrians in laboratory studies using the methods presented here. The developed methods, together with friction measurements made by FIOH, can provide a basis for establishing standard tests of anti-slip devices as personal protective equipment for leisure purposes. In addition, the intervention study indicates that use of anti-slip devices on icy/snowy surfaces can increase exposure without increasing risks, i.e. lead to increases in walking distance, with accompanying health benefits, while reducing rates of slipping and falling Anti-slip devices are recommended to be used for preventing slipping and falling on icy and snowy surfaces during the wintertime.

The experimental setup with the walking cycle was intended to resemble walking behaviour on five slippery surfaces in identified types of dangerous areas for pedestrians, but the surfaces used could be reduced to snow-covered ice, pure ice and salt on ice. The subjective methods used for measuring subjects’ perceptions of walking safety and walking balance seem to be appropriate and could be included in a standard test. The results of the tests also show that differences in movements in the rest of the body when walking with anti-slip devices were less frequent than variations in heel strike and toe off, indicating that analyses of movements in the rest of the body can be excluded. The methods used in this study were all convenient, functional and user-friendly, and can be used in a Nordic and/or European standard.

The current criteria for CE-approval are insufficient to exclude poorly working devices. What methods can be recommended in a European standard for anti-slip devices? The suggestion is that both subjective and objective methods should be used. The findings of the studies underlying this thesis indicate that standard tests of anti-slip devices should include the following: Rating scales for perceived safety and balance Measurements of walking time, step length and walking cycle duration A list of subjective priorities for individuals’ personal use A list of perceived advantages and disadvantages Measurements of coefficient of friction Measurements of the tensile strength of fastening parts and spikes/studs.

A heel device was selected as the best device in the first laboratory test. In the following laboratory tests, a whole-foot device appeared to be the best. However, in the last laboratory study, the whole-foot device did not fit properly to some of the subjects’ shoes, thus reducing the anti-slip support and a heel device was concluded to be the best device. Using a heel device may result in a more focused and gentle heel strike, and thus increase the heel device/surface area during heel touch-down, further explaining why the heel device was selected as the best in terms of walking safety and balance in the last laboratory test. Nevertheless, a whole foot device properly attached to the shoe is still considered to be the best type of device. A whole-foot device should support a normal gait with proper heel strike, gentle roll over and a safe toe off. Heel devices are the second best type for supporting a natural gait, and foot-blade devices are the best type for supporting a gait adopted by many women.

New anti-slip devices still need to be developed and designed with studs/pins located closer to the perimeter to ensure that good grip is provided, regardless of the part of the device that is in contact with the surface and the type of device it is.

The average daily total walking distance recorded in the studies is similar to the average distance recorded in national travel survey data. Access to anti-slip devices increases their use, and those using appropriate devices were found to walk further daily on average than non-users, thereby increasing their exposure.

Anti-slip devices do prevent people from falling. The risks of both incidents/falls and actual falls were found to be reduced by using anti-slip devices (by incident rate ratios of 0.67 and 0.64, respectively).

Thus use of anti-slip devices can increase people’s exposure without increasing their risk of having incidents/falls or actual falls.

The users of anti-slip devices stated that they will continue to wear them and they will also recommend others to do so. By reducing slip and falls during the wintertime, the single- pedestrian accidents can be reduced, thus improving pedestrians’ safety in the traffic environment.

By using appropriate anti-slip devices and providing information about when and where to use them (which depend on their design) frequencies of slips and falls can be reduced, with accompanying reductions in costs related to injuries of falling pedestrians. Hence, use of anti- slip devices is a cost-efficient traffic safety countermeasure, for reducing injuries from single- pedestrian accidents.

Aspects that warrant further research include verification of the effects of anti-slip devices on exposure and the occurrence of falls and their effects among specific groups such as the elderly.

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Appendix 1. Tested anti-slip devices and their properties

Foot blade devices

Device Acti- Name Construction Friction per Fastening Comments no. vation material shoe by ** (no. of edges) **** F1 d Halkej Polymer, steel Studs (3) Strapped over No strap around the DS=29,DF=52 the foot blade heel to prevent it slipping off. Three edges by the sole to prevent sliding. F2 d Yngsjö- Polymer, steel Steel edges (5 Elastic bands Four edges by the spike larger, 2 sole to prevent smaller) sliding DS=28,DF=51 F3 d Trönder Polymer, steel Steel edges (4) Strapped over Four edges by the DS=20,DF=41 the foot blade. sole to prevent Elastic bands sliding around the heel F4 d Conti Polymer, steel Studs (4) Elastic flat Spiky DS=31,DF=36 punched/cut out bands F5 d Ö-viks Polymer ring, Screw pin (3) Elastic polymer Three edges by the steel DS=2, DF=72 ring sole to prevent sliding F6 d Sport Leather, steel Steel edges Leather strap For use with a buckle kick-sled F7 d Sandy Polymer, Ceramics Elastic bands ceramics (sandpaper) F8 d Sandy with Polymer, Studs (5) + Elastic bands studs ceramics, steel ceramics (sandpaper) DS=16,DF=47 F9 d Rud Polymer, steel Chain welding Elastic bands Quickstep points (ca. 10) DS=15,DF=43 F10 f Conti- Sole pattern Mounted by contact DS=0, DF=0 shoemaker F11 d Dubby Polymer, steel Studs (5) Elastic bands DS=16,DF=47 **a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoemaker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe. **** DS = distance to the side of the shoe, DF = distance to the front of the shoe, DB = distance to the back of the shoe (in mm)

Heel devices

Device Acti- Name Construction Friction per Fastening Comments no. vation material shoe by ** (no. of edges) **** H1 a Cats Steel Steel wire tip Mounted by (2) shoemaker DS=20,DB=50 H2 a Rewa Steel Steel edges (2) Mounted by DS=18,DB=48 shoemaker H3 d Eissporn Polymer, steel Steel edges Strapped with (36) buckle DS=0, DB=0 H4 d Thulin Polymer, steel Steel edges Strapped with Two edges towards (18) buckle the sole to prevent DS=0, DB=0 sliding H5 a Panther Steel Steel (2) Mounted by Snow boots with DS=30,DB=43 manufacturer pre-mounted heel devices H6 d Frost Leather, Steel Steel edges Leather strap buckle H7 d Instant Special rubber Studs (4) Velcro© Reflex at the back stop mix with high fastening friction, steel, polymer H8 a Sure foot Steel Steel edges (4) Mounted by DS=24,DB=60 shoemaker **a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoemaker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe. **** DS = distance to the side of the shoe, DF = distance to the front of the shoe, DB = distance to the back of the shoe (in mm)

Whole-foot devices Device Acti- Name Con- Friction per shoe Fastening Comments no. vation struction by ** material (no. of edges) **** W1 f Studs Steel Studs (13) Mounted with a Studs used for DS=12, DF=23 special supplied predrilled DS=10, DB=20 tool wellingtons W2 f Glistop Chemicals: Uneven surface Spread under Health risk when Prepolymer DS=0, DF=0, the sole. Dry 24 applying MDI, Xylen DS=0, DB=0 hours. W3 d Metal Steel Perforated metal Bent metal Stiff, heavy rail (25 hole edges) DS=20, DF=10 DS=12, DB=15 W4 d Wish Polymer, Steel edges on Velcro© Stiff steel metal rail (22 steel fastening edges) DS=40, DF=80 DS=20, DB=0 W5 d Ice spike Polymer, Steel edges (12 + Buckle (the grip Two parts. The steel 24) handle works in foot blade device DS=8, DF=60 the opposite loosens when DS=0, DB=0 direction attaching W6 f Extra Rubber/ Sole pattern Mounted by polymer DS=0, DF=0, shoemaker DS=0, DB=0 W7 d Sensi Polymer, Spikes (14) Galosh Overshoe steel DS=29, DF=27 DS=26, DB=27 W8 d Ice Polymer, Steel edges (32) Velcro© gripper Steel DS=27, DF=52 fastening DS=12, DB=37 W9 a Beaver Steel Steel edges (4+4) Mounted by the Snow boot with DS=32, DF=40 manufacturer pre-mounted heel DS=26, DB=47 and foot blade device W10 d Icer’s/ SBR Replaceable studs Velcro© Heavy Stabilicer rubber, (17) fastening steel DS=10, DF=6 DS=9, DB=12 W11 d Berg- Polymer, Chain welding Elastic bands steiger steel points (ca. 20) DS=5, DF=39 DS=5, DB=35 W12 d Universal Polymer, Screw pins (5-20) Bootlace Prototype kit *** steel assembled by the user W13 f All stop Steel Steel cups (9) Mounted by Prototype DS=2, DF=15 user (glue and DS=2, DB=19 screws) W14 a APA Polymer, Studs (8) Velcro© Shoe steel DS=16, DF=48 fastening spikes DS=17, DB=35 **a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoemaker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe. *** device no. 29 is supplied as a kit that can be combined and used as a foot blade device, a heel device or as a combined whole foot device. **** DS = distance to the side of the shoe, DF = distance to the front of the shoe, DB = distance to the back of the shoe (in mm)

Appendix 2. Questionnaire

No … Date …

Background data

Gender: Male…… /Female ……… Age: ….. Weight: ….. Height: …..

What type of shoes do you use during winter time? ………………

What factors do you think are of importance for good winter shoes? ………………..

Do you have previous experiences of using anti-slip devices? ……………………..

Do you have problems when walking outdoors during the wintertime? No Yes, when it is cold Yes, when it is slippery Yes, when …. If yes, why?......

During the last seven days have you have had any problems (weaknesses/pain) in any of the following body parts?

Weak/shaky pain/ache no pain Shoulder/arm Spine Hip Knee Feet

What anti-slip device do you prefer on your winter shoes? Detachable? Fixed? Why?......

How do you judge your walking ability (put a mark on the line**) Without any problem Very large problems ______

How do you judge your balance (put a mark on the line**) Without any problem Very large problems ______

Ability for physical activities

A four grade scale, none, bad, fairly good, good, with possibilities for comments regarding: With eyes open, standing on one leg for more than 15 sec. Shutting one’s yes and standing on one leg more than 15 sec. Standing on the toes Standing on the heel Walking on heels

Ability to perform with or without problems (Yes/No): Hip flexion Knee extension Knee flexion

For each of the anti-slip devices and without using any anti-slip devices the following were registered:

Device no …. Time to put on:…. (sec) Time to take off: …. (sec) Exertion: …… (Borg scale*)

Perceived walking safety on Sand Gravel Snow Ice Salt None Bad Fairly good Good

Time to traverse across all tracks: ……(sec)

Perceived walking balance on Sand Gravel Snow Ice Salt None Bad Fairly good Good

Easiness to take off and put on……….. Advantages with this device……….. Disadvantages with this device…… Other opinions about this device…

*The Borg Scale is a simple method of rating perceived exertion (RPE) The RPE-scale is a scale with figures ranging between 11, 12, ..., 19, 20. 11 indicates no exertion at all and 20 extreme exertion. (The figures x10 can be expected to correspond to the actual pulse of the subject). ** The line is 10 cm long on the form the subject uses.

Appendix 3. Daily diary

Contributions to the papers

The author of this thesis, Glenn Berggård, contributed to the papers as the principal investigator for all the tests, through major involvement in the selection of methods, planning and utilization of the tests, in the analysis of the data and the writing of all the papers. I was the corresponding author/main author for Papers III, IV, VI and VII, the sole author of paper IV, and the corresponding author/main author for Papers I, II and V. Gunvor Gard was responsible for the analyses of the video recordings and the statistical analysis of responses to the questionnaires used to obtain the data analysed in Papers I, II, III and V/VI. I was responsible for the statistical analysis presented in Paper VII. More detailed contributions are listed below on a per-paper basis.

Paper I I initiated the project, planned the project together with Gunvor Gard and was the principal investigator. I participated in the data collection, Gunvor Gard was responsible for most of the literature review, the objective analysis, and the statistical analysis. I analyzed the data together with Gunvor Gard, and participated in the writing of the paper.

Paper II I initiated the project, planned it together with Gunvor Gard, was the principal investigator and participated in the data collection. Gunvor Gard was responsible for most of the literature review, the objective analysis, and the statistical analysis. I analyzed the data together with Gunvor Gard and participated in the writing of the paper.

Paper III I initiated the project, planned it together with Gunvor Gard, was the principal investigator and participated in the data collection. Gunvor Gard was responsible for the objective analysis and statistical analysis. I evaluated the results, wrote most of the paper, and did did most of the literature review.

Paper IV I did the literature review, all the work and wrote the paper.

Paper V I initiated the project, planned it together with Gunvor Gard, was the principal investigator and participated in the data collection. Peter Jäger carried out most of the practical data collection and recording for further statistical analysis. Gunvor Gard was responsible for the objective analysis and statistical analysis. Together with Gunvor Gard I analyzed the data and wrote the paper.

Paper VI I initiated the project, planned it together with Gunvor Gard and was the principal investigator. Most of the project was planned and prepared in the study presented in Paper V. Carita Aschan and Mikko Hirvonen made the laboratory tests at FIOH and supplied the data for joint analysis. I was responsible for most of the literature review and writing most of the paper. Carita Aschan and Mikko Hirvonen wrote the part about the laboratory test at FIOH. Carita Aschan, Mikko Hirvonen and Gunvor Gard contributed comments on drafts of the paper.

Paper VII I initiated the project, planned it and was the principal investigator. Charlotta Johansson and Anders Lagerkvist participated in the planning of the project. Gunvor Gard, Charlotta Johansson and Anders Lagerkvist participated in discussions about methods to use. I collected all the data, analyzed the statistics, reviewed the literature and wrote most of the paper. Charlotta Johansson participated in the analyses of the results and writing of the paper. Karin Brundell-Freij gave valuable comments on the statistical analysis and drafts of the paper. Anders Lagerkvist, Lars Leden and Per Gårder also made valuable comments on drafts of the paper.

Paper I Accident Analysis and Prevention 33 (2001) 1–8 www.elsevier.com/locate/aap

Test of Swedish anti-skid devices on ﬁve different slippery surfaces

Gunvor Gard a,*, Glenn Lundborg b

a Department of Musculoskeletal Diseases, Di6ision of Physiotherapy, Lund Uni6ersity, Box 5134, 220 05 Lund, Sweden b Department of En6ironment Planning and Design, Lulea˚ Uni6ersity of Technology, 971 87 Lulea˚, Sweden Received 30 June 1999; accepted 18 November 1999

Abstract

The interest for effective preventive strategies for slips and falls is growing. Much remains to be done, however, to prevent slips and falls in the trafﬁc environment. Some pedestrians are injured because of slippery pavements and roadways. Using an appropriate anti-skid device may reduce the risk of slips and falls on different surfaces outdoors during winter. The aim of this study was to evaluate new anti-skid devices on the Swedish market representing three different designs of anti-skid devices; heel device, fore-foot device and whole-foot device on different slippery surfaces, gravel, sand, salt, snow and ice. The evaluations were done according to subject’s perceived walking safety and balance, videorecordings of walking postures and movements, time to take on and off each anti-skid device, advantages/disadvantages with each anti-skid device and a list of priority for own use according to three criteria; safety, balance and appearance. Practical tests were carried out on different slippery surfaces, gravel, sand, salt, snow and ice. The subject’s were randomly selected from the registered population over 55 years in a city in northern Sweden. The results showed that eight or more of the ten subjects perceived all four anti-skid devices as fairly good or good regarding walking safety and balance when walking on gravel, sand, and salt. Anti-skid device 3, a whole-foot device was perceived as having none or bad walking safety and balance on snow by seven subjects and anti-skid device 4, a heel device, as having none or bad walking balance on ice by all ten subjects. Eight subjects walked with a normal muscle function in the hip and knee with all anti-skid devices on all surfaces. Small deviations in walking posture and movements were noted in one to two subjects when walking on different surfaces, but no systematic difference between the devices. Anti-skid device 1 ‘Rewa’, a ﬁxed heel device, was perceived as the most rapid one to take on. All four devices were perceived as easy to use and as giving good foothold. Anti-skid device 1 ‘Rewa’ and 4 ‘Thulin-spike’, both heel devices, had the highest priority according to walking safety. ‘Rewa’ also had the highest priority according to walking balance as well as own use. When combining the criterias ‘Rewa’ had the highest priority according to walking safety and balance, priority for own use, time to take on and easiness to use. © 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Anti-skid devices; Slippery surface; Safety

1. Introduction 1-year period showed that the main categories of injury were falls (52%), vehicle-associated events (44%) and The interest for effective preventive strategies for other injury events (4%). In women, falls were a more slips and falls is growing (Nagata, 1991; Redfern and common cause of injury than vehicle events, whilst in Bloswick, 1997; Gro¨nqvist, 1999). Much remains to be men there was a tendency for a converse relationship done, however, to prevent slips and falls for people in (Sjo¨gren and Bjo¨rnstig, 1991). Two thirds of the falls the traffic environment. Some pedestrians are injured because of slippery pavements and roads. A lot more involved slipping on ice and snow. Ice- and snow-re- pedestrians choose to stay inside during slippery lated injuries (all categories) accounted for 37% of the weather. An analysis of 297 persons aged over 60 total cost of all injuries in the elderly in the traffic treated for injuries in the traffic environment over a environment in Sweden (Sjo¨gren and Bjo¨rnstig, 1991). The number of injuries increased as people grew older, and women in their 50’s showed the highest percentage. * Corresponding author. Tel.: +46-46-2224108; fax: +46-46- 2224202. Lund (1984) estimated that in Denmark, Finland, Nor- E-mail address: [email protected] (G. Gard). way and Sweden the costs of accidents involving falls

0001-4575/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII: S0001-4575(00)00002-6 2 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 were of the same magnitude as those of traffic acci- the body weight on the slipping foot and allows the dents, mainly because of the long treatment times for sliding movement to continue into a fall (Gro¨nqvist, elderly people with hip fractures. He anticipated that 1995). foot slippage caused 43% of all falls and 16% of all Studies have been done on assessing the anti-slip accidents at work, in the home and during leisure properties of different types of winter shoes, on wet and activities in the Nordic countries. Two thirds of these on dry icy surfaces (Gro¨nqvist, 1995). Slip resistance slips occurred on pavements or other surfaces covered has been assessed by objective friction measurements by ice and snow (Lund, 1984). and by subjective methods (paired comparisons). A In Sweden the number of people over the age of 65 is friction measurement apparatus and a method for as- expected to increase by 10% and to make up about 20% sessing slip resistance of the heels and soles of footwear of the population in the beginning of the next century on icy surfaces have been developed for laboratory use (SCB, 1987). Reduced postural control, i.e. disturbed (Gro¨nqvist, 1995). Comparative studies of friction mea- balance, has been put forward as a background factor surement devices show that a few devices are capable of to falls in the elderly (Tinetti et al., 1988). Reduced simulating closely the force and motion in human gait muscle strength in the lower extremities (Brocklehurst (Gro¨nqvist, 1995). A method for estimating the proba- et al., 1978) and reduced mobility and function (Wild et bility of slips and falls based on measurements of al., 1981) have also been found to be background available and required friction has been developed by factors to falls in the elderly. Hansson et al. (1999). The dynamic coefficient of fric- The risk of slipping and falling depend also to a great tion (DCOF) of shoe, floor surface and contaminant extent on a person’s subjective awareness of the poten- interfaces were measured. Required friction was as- tial slipperiness of the actual conditions. It may be sessed by examining the foot forces during walking easier to adapt one’s gait when a slippery condition is trials when no slips occurred. Slips with recoveries and steady than when unexpected changes in slipperiness slips resulting in falls were recorded and categorized occur. However no accident or injury statistics are using a force plate and high-speed video camera. The available to confirm this hypothesis (Gro¨nqvist, 1999). results showed that the number of slips and fall events It has been shown by Merrild and Bak (1983) that increased as the difference between the required and the certain high-risk winter days can cause enormous in- measured coefficient of friction increased. This type of crease of pedestrian injuries due to falls initiated by measurements and analysis could be used to evaluate slipping. slip resistance measurement devices under various con- There are five critical motor functions during the gait ditions and assist in the design of safer environments cycle in order to achieve safe propulsion of the body (Hansson et al., 1999). (Winter, 1991). These functions are the maintenance of In Europe the work concerning EC type-examination support of the body during stance, the maintenance of upright posture and balance of the total body, the and certification of Personal Protective Equipment for control of foot trajectory to achieve safe ground clear- anti-slip protection (also called anti-skid devices) is ance and gentle heel or toe landing, the generation of mainly the responsibility of CEN Technical Committee mechanical energy to maintain the present forward TC 161 (foot and leg protectors). The essential health velocity or to increase the forward velocity and finally and safety requirements for the design, construction the absorption of mechanical energy for shock absorp- and manufacturing of personal protective equipment tion and stability or to decrease the forward velocity of including anti-skid devices are set forth in the directive / / the body (Winter, 1991). 89 686 EEC and its amendments, whereas the Eu- Risk factors for slips and falls may be extrinsic ropean standards have been worked out to devise prac- (environmental factors) or intrinsic (human factors) or tical solutions as how to harmonize those essential mixed (system factors) (Gro¨nqvist, 1995). The primary requirements. Currently there are no standards for anti- risk factor for slipping accidents is according to Gro¨n- skid devices, wherefore these have been assessed di- qvist, poor grip and low friction between the footwear rectly against the essential health and safety (foot) and the underfoot surface (pavement). From the requirements stipulated in the Council Directive 89/686/ slipping point of view there are two critical gait phases EEC (Gro¨nqvist and Ma¨kinen, 1997). There is an ur- in walking; heal-strike and toe-off (Strandberg and gent need to develop European harmonized standards Lanshammar, 1981). The heel-strike causes a forward for anti-skid devices in use by workers at the workplace slip on the leading foot, whereas the toe-off causes a as well as for the elderly pedestrians and for other backward slip on the sole forepart, which can be coun- private users. The focus of the standard should be on teracted by stepping forwards with the leading foot. assessing the preventive effect of the device, including The forward slip starting at heel-strike, would very ergonomic and functional aspects. There is a need for likely result in a dangerous fall backwards, due to the subjective and functional methods for testing and eval- fact that the forward momentum of the body maintains uating safety aspects of anti-skid devices. G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 3

Using an appropriate anti-skid device as a pedestrian strength were measured before the experiment by an may prevent the risk of slips and falls on ice and snow. experienced physical therapist and compared to normal When trying to improve the function of anti-skid values. The anti-skid devices were new on the Swedish devices and the possibilities of safe pedestrian move- market and represented three different designs of anti- ment during winter, methods to test anti-skid devices skid devices; heel device, fore-foot device and whole- need to be developed. foot device (Figs. 1–2). The sequence of the devices was The aim of this study was to evaluate new anti-skid randomized for each subject. The subjects had no ear- devices on the Swedish market representing three differ- lier experience from walking with the anti-skid devices. ent designs of anti-skid devices; heel device, fore-foot For the practical tests ﬁve different walking areas device and whole-foot device on ﬁve different slippery with different slippery surfaces, each 10 m long, were surfaces. prepared:

Ice with sand (180 g/m2) / 2 2. Material and methods Ice with gravel (4–8 mm ca. 150 g m ) Ice with 3–5 mm snow Ice 2.1. Material Ice with salt (9 g/m2) To evaluate realistic walking situations in the traffic Ten subjects, randomly selected from the registered environment, such as a pedestrian crossing, the walking population in Lulea˚over 55 years, five women and five cycle for each walking area was divided into six parts: men, participated in the test of the four anti-skid 1. Walk ‘normally’ across the whole area devices. The mean age of the subjects was 62.4 years. 2. Turn around Inclusion criteria for participation in the experiment 3. Walk rapidly 4–5 steps were also normal balance in walking, normal mobility 4. Stop in hip, knee and foot and normal muscle strength in the 5. Walk backwards 4–5 steps lower extremities. Balance, mobility and muscle 6. Walk ‘rapidly’ across the whole area Before the test each subject had the opportunity to walk without anti-skid device on these six parts of the experimental walking cycle without stress so they were familiar with the situation. The subjects could use helmet if they wanted in the experiment. No other safety precautions were taken. In the test situation each subject walked with each anti-skid device on the five different slippery surfaces. The subjects were told to walk according to the instructions above. When the experiments were performed the out-door temperature was −5°C and it was daylight (Fig. 3). After each practical test the subjects rated their walking safety and walking balance on each surface and described perceived advantages and disadvantages with Fig. 1. Anti-skid devices 1–4; Rewa, Yngsjo¨-spike, metal rail and each anti skid device. After the tests, the subjects own Thulin-spike (from top left, top right, bottom left to bottom right). priorities regarding safety, balance and appearance were noted.

2.2. Methods

Methods used in this study were rating scales for perceived walking safety and balance, observations from videorecordings of walking postures and movements, time to take on and off each anti-skid device, advantages/disadvantages with each anti-skid advice and a list of priority according to three criteria; safety, balance and appearance/own use. These methods have been developed earlier to describe functional problems Fig. 2. Principal design of the anti-skid devices; 1 is a ﬁxed heel in walking with different anti-skid devices (Gard and device, 2 a fore-foot device, 3 a whole-foot device and 4 a heel device. Lundborg, 1999). The rating scales for perceived walk- 4 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8

Fig. 3. The experimental set-up. Each track is 10 m long and 1 m wide. Some of the tracks are covered with different material such as gravel, sand, snow and salt. ing safety and walking balance were ﬁrst developed and 3. Results tested for reliability (Figs. 4 and 5). Interreliability test of these scales were done from videorecordings of walk- 3.1. Walking safety and balance ing with different anti-skid-devices on different surfaces in the experimental situation described below by two Eight or more of the subjects perceived all anti-skid experienced physical therapists. The interreliability of devices as fairly good or good regarding walking safety the walking safety and balance scales were measured as and balance when walking on gravel, sand, and salt the percentage of agreement between the physical thera- (Tables 1 and 2). Concerning walking safety on snow pists when observing videorecordings of all subjects in anti-skid device 3 was perceived as having none or bad all tests. The percentage of agreement of the walking walking safety by seven subjects (Table 1). Concerning safety scale was 86% and the corresponding agreement walking balance anti-skid device 3 was perceived as of the walking balance scale was 88% (Gard and Lund- having none or bad walking balance on snow and borg, 1999). anti-skid device 4 as having none or bad walking Four rating scales for evaluation of observed walking balance on ice (Table 2). movements have also been developed (Fig. 6) (Gard and Lundborg, 1999). The rating scales were developed 3.2. Mo6ement analyses by a physical therapist, trained in movement analysis. The dimensions evaluated were: (1) walking posture Eight or more subjects walked with a normal muscle and movements including normal muscle function in function in the hip and knee with all anti-skid devices the hip and knee; (2) walking posture and movements on all surfaces (Table 3). Two subjects walked with in the rest of the body (head, shoulders and arms); (3) straight knees without swaying with anti-skid device 1, heel-strike; and (4) toe-off. All four dimensions were 2 and 3 on ice, and one subject had the same movement evaluated by observation scales ranging from 0 to 3 (Fig. 6). Interreliability test of these scales were done from videorecordings of walking with different anti- skid-devices on different surfaces in the experimental situation described below by two experienced physical therapists. The interreliability of the four observation scales were measured as the percentage of agreement between the physical therapists when observing vide- Fig. 4. Rating scale for ratings of perceived walking safety. orecordings of all subjects in all tests. The percentage of agreement between the physical therapists in the four observations scales were 85, 80, 86 and 85%, respectively (Gard and Lundborg, 1999). Another measure developed was the subjective choice of an anti-skid device for own use. Each subject made a list of priority according to three criteria; safety, balance and appearance (Gard and Lundborg, 1999). Fig. 5. Rating scale for ratings of perceived walking balance. G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 5

Fig. 6. Observation of walking posture and movements in different parts of the body, heel-strike and toe-off.

Table 1 The subjects (N=10) perceptions of walking safety after walking with each of the anti-skid devicesa

G SA SN IST

D R YMTRYMTRYMT RYMTRYMT

N 1131 11 1 B 2 21 2 316 4 332 43 FG 3 44 31 4662 5 67554943 5G 4 5 5 9 10 10 5 1 33167

a 1, Rewa; 2, Yngsjo¨; 3, metal; 4, Thulin on gravel (G), sand (SA), snow (SN), ice (I) and salt (ST). Walking safety was evaluated as none (N), bad (B) fairly good (FG) or good (G). Anti-skid device 1 and 4 were heel devices, 2 was a fore-foot device and 3 was a whole-foot device.

Table 2 The subjects (N=10) perceptions of walking balance after walking with each of the anti-skid devicesa

G SA SN I ST

R YMTRYMTRYMTRYMTRYMT

N 111 111 1 B 1 11 256 544 9 2 FG 3 54 5152 5612 3 416 667 4 G9645 4 58 5231 1144 443 4

a 1, Rewa; 2, Yngsjo¨; 3, metal; 4, Thulin on gravel (G), sand (SA), snow (SN), ice (I) and salt (ST). Walking balance was evaluated as none (N), bad (B) fairly good (FG) or good (G). 6 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 pattern on snow when walking with all anti-skid devices two subjects when walking with all anti-skid devices on (Table 3). Small deviations in walking posture and all surfaces but no characteristic pattern of the devia- movements were noted in the rest of the body. Most tions (Table 6). deviations were noted when walking with device 1 on gravel and device 2 and 3 on ice (Table 4). Some deviations were also noted in heel-strike. Deviations 3.3. Time to take on/off and ad6antages/disad6antages from normal heel-strike were mainly shown when walking with device 2, 3 and 4 on ice (Table 5). Small Anti skid device 1 was perceived as the most rapid deviations from normal toe-off were shown in one to one to take on and device 3 and 4 as the most rapid

Table 3 Number of subjects with different observations (0–3) concerning walking posture and movements including normal muscle function in the hip and knee (N=10)a

De R R RRR Y Y YYY MMM MMTTTTT Su 1 2345123451234 5 12345

891010108910100 10 10891010 10 9 91010 1112 21211 2 3

a De, device number 1–4; Su, surface number (1, gravel; 2, sand; 3, snow; 4, ice; and 5, salt). The observed ratings 0–3 are deﬁned in Fig. 6.

Table 4 Number of subjects with different observations concerning walking posture and movements including movements in the rest of the body (head, shoulders and arms) (N=10)a

DeR R RRRYYYYYMMMMMTTTTT Su 1 2 3 45123451 2 3514 2 345

0 7 7658797484 9 4 4 8 8 88610 123334 213425 1 5 4 2 2223 2211211 1 1 3

a De, device number 1–4 (1, Rewa; 2, Yngsjo¨; 3, metal and 4, Thulin), Su, surface number (1, gravel; 2, sand; 3, snow; 4, ice; 5, salt). The observed ratings 0–3 are deﬁned in Fig. 6.

Table 5 Number of subjects with different observations concerning heel-strike (N=10)a

DeR R RRRY YYYYMMMMMTTTTT 1Su 223 15432154 3 4215 345

0 6 895910983871084 8 10 10 9 5 10 113215 12522 2 5 1 13 21 2 1 11 2 3

a De, device number 1–4 (1, Rewa; 2, Yngsjo¨; 3, metal; 4, Thulin), Su, surface number (1, gravel; 2, sand; 3, snow; 4, ice; 5, salt. The observed ratings 0–3 are deﬁned in Fig. 6.

Table 6 Number of subjects with different observations concerning toe-off (N=10)a

De R RRRRYYYYYMMM MMTTTTT Su1234 5 123451234512345

0455 55555565 5 5 5 555 555 1 3 434333333344433 3333 2 3 12122222121112222 2 2 3

a De, device number 1–4; Su, surface number (1, gravel; 2, sand; 3, show; 3, ice; 5, salt). The observed ratings 0–3 are deﬁned in Fig. 6. G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 7

Table 7 4. Discussion Time to take on and off the anti-skid devicesa

Device Rewa Yngsjo¨ Metal Thulin Eight or more of the subjects perceived all anti-skid devices as fairly good or good regarding walking safety Time to take6 (2–10) 11 (5–25) 9 (5–15) 13 (2–20) and balance when walking on gravel, sand, and salt. on Anti-skid device 3 was perceived as having none or bad Time to take 6 (2–20) 7 (3–15) 4 (2–10) 4 (2–10) walking safety and balance on snow by seven subjects off and anti-skid device 4 as having none or bad walking a 1, Rewa; 2, Yngsjo¨; 3, metal; 4, Thulina. Mean values (range) in balance on ice by all ten subjects. Eight subjects walked seconds for the ten subjects. with a normal muscle function in the hip and knee with all anti-skid devices on all surfaces. Small deviations in Table 8 walking posture and movements were noted in one to All possible advantages and disadvantages mentioned two subjects when walking on different surfaces, but no Rewa systematic difference between the devices. Anti-skid Advantages Easy to use, stable to walk with, good foothold device 1 ‘Rewa’ was perceived as the most rapid one to take on. All four devices were perceived as easy to use Disadvantages Heel-strike unstable on ice and snow and as giving good foothold. Anti-skid device 1 ‘Rewa’ Yngsjo¨ and 4 ‘Thulin-spike’ had the highest priority according Advantages Easy to use, good foothold to walking safety. ‘Rewa’ had the highest priority ac- Disadvantages Heel-strike unstable, walk on fore-foot cording to walking balance and also the highest priority Metal according to own use. Advantages Easy to use, good foothold, easy to adjust When combining the criterias, the result show that Disadvantages Clumsy device 1 ‘Rewa’ had the highest priority according to all Thulin criterias: walking safety and balance, own use, time to Advantages Good foothold, easy to use take on and easiness to use. ‘Rewa’ was a fixed heal Disadvantages Need heel-strike, unstable fore-foot, parts can device. Although it is not a whole foot device, it seemed get loose, uncomfortable to walk with to be very stable and comfortable to walk with and there were no parts that could come loose during the walking. Table 9 When observing the walking posture and movements Subject’s first priorities according to own use concerning walking including normal muscle function in the hip and knee, safety, walking balance and choice for own use (N=10) all subjects showed a normal pattern when walking with ‘Rewa’ on gravel, sand and salt and only minor devia- DeviceR Y M T tions were shown on snow and ice. The primary risk Walking safety4 2 4 factor for slipping accidents according to Gro¨nqvist Walking balance 7 3 (1995) is poor grip and low friction between the Choice for own use 73 footwear (foot) and the underfoot surface (pavement). As regards heel-strike and toe-off, the most relevant parts of the walking cycle in relation to slipping risk (Strandberg and Lanshammar, 1981) only minor deviations were shown when walking with ‘Rewa’. In the experimental situation, the rating scales for describing perceived safety and balance, the observation ones to take off (Table 7). All four devices were per- methods, the measures to choose an anti-skid device for ceived as easy to use and as giving good foothold. own use and to list perceived advantages and disadvan- Disadvantages mentioned were that device 1 and 2 gave tages were functional and practical and could be recom- unstable heel-strike and that device 4 gave unstable mended for further use. These practical measures show forefoot (Table 8). how to increase the usability of the anti-skid devices. The experimental set-up with five slippery surfaces is 3.4. Choice for own use a realistic situation and the sequence of the devices was randomized for each subject. No specific safety precau- Each subject’s choice of an anti-skid device for own tions were taken during the experiment. This may have use according to three criterias; walking safety, walking reduced the walking pace to a slower pace in the balance and choice for own use was registered. Anti-skid ‘walking rapidly-phase’ compared to if safe precautions device 1 and 4 had the first priority according to walking had been arranged. As a precaution in this study the safety, device 1 according to walking balance and device subjects had the opportunity to walk without anti-skid 1 according to own use (Table 9). devices on the surfaces before the experiments. Before 8 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 33 (2001) 1–8 future experiments precautions have to be discussed References and if possible arranged. The study took place on a constructed ice area outside a laboratory. The area Brocklehurst, J.C., Exton-Smith, A.N, Barber, S.M., Hunt, L.P., was slightly inclined sideways (0.25%),which is approx- Palmer, M.K., 1978. Fracture of the femur in old age: a two-centre study of associated clinical factors and the cause of the fall. Age imately the same as a normal sidewalk in Sweden. The Aging 7, 7–15. ice surface was even. Not rough or covered with Gard, G., Lundborg, G., 1999. Pedestrians on slippery surfaces during tracks from cars as it normally might be. This is winter-methods to describe the problems and practical tests of representative from all kinds of slippery surfaces. Fur- anti-skid devices. Accident Analysis and Prevention (in press). ther studies ought to be done on other surfaces such Gro¨nqvist, R., 1995. A dynamic method for assessing pedestrian slip resistance. Thesis. Finnish Institute of Occupational Health, as surfaces made from hard packed snow, rough sur- Helsinki. faces, inclined surfaces in the walking direction (2, 5, 8 Gro¨nqvist, R., 1999. Slips and falls. In: Kumar, S. (Ed.), Biomechanics and above 8%). No more than 2% is supposed to be a in Ergonomics (Ch. 19). Taylor and Francis, London. good standard for walk- and bike-roads close to cross- Gro¨nqvist, R., Ma¨kinen, H., 1997. Development of standards for ing and 5 and 8% are slope standards for adopting the anti-slip devices for pedestrians. In Fifth Scandinavian Symposium on Protective Clothing, May 5–8, 1997, Elsinore, Denmark. special requirements for disabled people in Sweden. Hansson, J., Redfern, M., Mazumdar, M., 1999. Predicting slips and The interest for preventive strategies for slips and falls considering required and available friction. Ergonomics 42. falls is growing (Nagata, 1991; Redfern and Bloswick, Lund, J., 1984. Accidental falls at work, in the home and during leisure 1997; Gro¨nqvist, 1999). It is important to make activities. Journal of Occupational Accidents 6, 181–193. anti-skid devices as safe, comfortable an practical as Merrild, U., Bak, S., 1983. Anexcess of pedestrian injuries in icy conditions: a high risk fracture group — elderly women. Accident possible. In our opinion it is also important to use Analysis and Prevention 15, 41–48. both subjective and objective research methods in the Nagata, H., 1991. Analysis of fatal falls on the same level or on work to develop European standards for anti-skid stairs/steps. Safety Science 14, 213–222. devices. Anti-skid devices need to be user-friendly to Redfern, M., Bloswick, D., 1997. Slips,Trips and Falls. In: Nordin, M., be used. Andersson, G., Pope, M. (Eds.), Musculosceletal Disorders in the Workplace. Masby Year Inc, pp. 152–166. SCB, Official report of statistics. Stockholm, 1987. Sjo¨gren, H., Bjo¨rnstig, U., 1991. Injuries to the elderly in the traffic 5. Conclusion environment. Accident Analysis and Prevention 23, 77–86. Strandberg, L., Lanshammar, H., 1981. The dynamics of slipping accidents. Journal of Occupational Accidents 3, 153–162. The anti-skid device 1 ‘Rewa’, had the highest prior- Tinetti, M.E., Speechley, M., Ginter, S.F., 1988. Risk factors for falls ity according to walking safety and balance, choice for among elderly persons living in the community. New England own use and time to take on. ‘Rewa’ was a fixed heal Journal of Medicine 26, 1701–1707. device. Although it is not a whole foot device, it Wild, D., Nayak, U.S.L., Isaacs, B., 1981. How dangerous are falls in old people at home? British Medical Journal 282, 266–268. seemed to be very stable and comfortable to walk with Winter, D.A., 1991. The Biomechanics and Motor Control of Human and there were no parts that could come loose during Gait: Normal, Elderly and Pathological, 2nd edn. University of the walking. Waterloo, Canada.

Paper II Accident Analysis and Prevention 32 (2000) 455–460 www.elsevier.com/locate/aap

Pedestrians on slippery surfaces during winter—methods to describe the problems and practical tests of anti-skid devices

Gunvor Gard a,b,*, Glenn Lundborg a,b

a Department of Musculoskeletal Disorders, Lund Uni6ersity, Box 5134, 220 05 Lund, Sweden b Department of En6ironment Planning and Design, Lulea˚Uni6ersity of Technology, 971 87 Lulea˚, Sweden Received 4 January 1999; received in revised form 12 April 1999; accepted 18 May 1999

Abstract

Every year there are thousands of pedestrians in Sweden who are injured because of slippery pavements and roadways. Using an appropriate anti-skid device may reduce the risk of slips and falls on ice and snow. Methods to describe functional problems in walking on different slippery surfaces during winter have been developed as rating scales for evaluating walking safety and walking balance and an observation method to observe posture and movements during walking. Practical tests of all 25 anti-skid devices on the market in Sweden were carried out on different slippery surfaces; gravel, sand, salt, snow and ice. The anti-skid devices were described according to the subjects’ perception of walking safety, walking balance and priority for own use. The postures and movements during walking were analysed by an expert physical therapist. The wholefoot device ‘studs’ was perceived as the best according to walking safety and walking balance and had the highest priority for own use. © 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Slippery surfaces; Pedestrians; Anti-skid devices

1. Introduction total cost of all injuries in the elderly in the traffic environment in Sweden (Sjo¨gren and Bjo¨rnstig, 1991). Interest and concern about the safety of old people in In Sapporo, Japan, most of the accidents during winter all types of environments is growing (Waller, 1978; (December, January and February 1984–1989) hap- Winter, 1984; Sjo¨gren and Bjo¨rnstig, 1989). Much re- pened on sidewalks (Hara et al., 1991).The number of mains to be done, however, to draw attention to the injuries increased as people grew older, and women in problem of the elderly in the traffic environment. Some their 50’s showed the highest percentage. Lund (1984) pedestrians are injured because of slippery pavements estimated that in Denmark, Finland, Norway and Swe- and roads (Honkanen, 1982; Merrild and Bak, 1983). A den the costs of accidents involving falls were of the lot more pedestrians choose to stay inside during slip- same magnitude as those of traffic accidents, mainly pery weather. An analysis of 297 persons aged over 60 because of the long treatment times for elderly people treated for injuries in the traffic environment over a with hip fractures. He anticipated that foot slippage 1-year period showed that the main categories of injury caused 43% of all falls and 16% of all accidents at were falls (52%), vehicle-associated events (44%) and work, in the home and during leisure activities in the other injury events (4%). In women falls were a more Nordic countries. Two thirds of these slips occurred on common cause of injury than vehicle events, whilst in pavements or other surfaces covered by ice and snow men there was a tendency for a converse relationship (Lund, 1984). (Sjo¨gren and Bjo¨rnstig, 1991). Two thirds of the falls In Sweden the number of people over the age of 65 is involved slipping on ice and snow. Ice- and snow-re- expected to increase by 10% and to make up about 20% lated injuries (all categories) accounted for 37% of the of the population in the beginning of the next century (SCB, 1987). Reduced postural control, i.e. disturbed * Corresponding author. Fax: +46-46-222-4202. balance, has been put forward as a background factor E-mail address: [email protected] (G. Gard) to falls (Tinetti et al., 1988). Reduced muscle strength

0001-4575/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII: S0001-4575(99)00070-6 456 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 32 (2000) 455–460 in the lower extremities (Brocklehurst et al., 1978) and reduced mobility and function (Wild et al., 1981) have also been found to be background factors to falls in the elderly. Preventing injuries in the elderly seems to be important, trying to reduce expected increases in costs for the health care system. Sjo¨gren and Bjo¨rnstig (1991) pointed out that special schemes are needed aimed at Fig. 1. removing ice and snow, reducing slipperiness by spreading sand and salt. Using an appropriate anti-skid device 89/686/EEC and its amendments, whereas the Eu- as a pedestrian may prevent the risk of slips and falls ropean standards have been worked out to devise prac- on ice and snow (Gro¨nqvist and Ma¨kinen, 1997). tical solutions as how to harmonise those essential Risk factors for slips and falls may be extrinsic requirements. Currently there are no standards for anti- (environmental factors) or intrinsic (human factors) or skid devices, wherefore these have been assessed di- mixed (system factors) (Gro¨nqvist, 1995). The primary rectly against the essential health and safety risk factor for slipping accidents is according to Gro¨n- requirements stipulated in the Council directive 89/686/ qvist, poor grip and low friction between the footwear EEC (Council Directive, 1989; Gro¨nqvist and Ma¨kinen, (foot) and the underfoot surface (pavement). As regards 1997). There is an urgent need to develop European slipping risk, the heel-strike and the toe off appear to harmonised standards for anti-skid devices in use by be the most critical phases in walking. The heel-strike workers at the workplace as well as for the elderly causes a forward slip on the leading foot, whereas the pedestrians and for other private users. The focus of the toe-off causes a backward slip on the sole forepart, standard should be on assessing the preventive effect of which can be counteracted by stepping forwards with the device, including ergonomic and functional aspects. the leading foot. The forward slip starting at heel- There is a need for subjective methods for testing and strike, would very likely result in a dangerous fall evaluating safety aspects of anti-skid devices. backwards, due to the fact that the forward momentum Using an appropriate anti-skid device as a pedestrian of the body maintains the body weight on the slipping may prevent the risk of slips and falls on ice and snow. foot and allows the sliding movement to continue into When trying to improve the function of anti-skid a fall. devices and the possibilities of safe pedestrian move- Studies have been done on assessing of the anti-slip ment during winter, methods to test anti-skid devices properties of different types of winter shoes, on wet and need to be developed. on dry icy surfaces (Gro¨nqvist, 1995). Slip resistance The first aim of this study was to describe methods has been assessed by objective friction measurements developed to rate and observe functional problems in and by subjective methods (paired comparisons). A walking on slippery surfaces during winter. The second friction measurement apparatus and a method for as- aim was to test and to describe the results from the test sessing slip resistance of the heels and soles of footwear of all 25 anti-skid devices on the Swedish market on on icy surfaces have been developed for laboratory use different slippery surfaces. (Gro¨nqvist, 1995). Devices for assessing footwear friction on ice, seem to be very rare. Two test rigs have been found. The first test was conducted at an ice 2. Methods to describe functional problems in walking skating rink and the frictional force was measured by a load cell at a low sliding velocity (Bruce et al., 1986). In Methods were developed to describe functional prob- the second test the load cell was positioned between the lems in walking with different anti-skid devices. First, subject’s belt and the springs. The recorded force was a rating scales for perceived walking safety and walking measure of the frictional force between the shoe and the balance were developed and tested for reliability (Figs. substrate (Manning et al., 1991). Comparative studies 1 and 2). Inter-reliability test of these scales were done of friction measurement devices show that few devices from video-recordings of walking with different anti- are capable of simulating closely the force and motion skid-devices on different surfaces in the experimental in human gait (Gro¨nqvist, 1995). situation described below by two experienced physical In Europe the work concerning EC type-examination and certification of Personal Protective Equipment for anti-slip protection (also called anti-skid devices) is mainly the responsibility of CEN Technical Committee TC 161 (foot and leg protectors). The essential health and safety requirements for the design, construction and manufacturing of personal protective equipment including anti-skid devices are set forth in the directive Fig. 2. G. Gard, G. Lundborg / Accident Analysis and Pre6ention 32 (2000) 455–460 457

dorsal-flexion of the foot take a step by flexion of the hip; 1, some heel-strike, try to take a step by dorsalflexion of the foot; 2, fairly good dorsal-flexion of the foot; and 3, very good dorsal-flexion of the foot. In the fourth observation scale toe-off was observed and classified according to: 0, no toe-off, no plantarflexion of the foot or extension of the hip; 1, some toe-off, try to take a step by plantar-flexion of the foot; 2, fairly good plantar-flexion of the foot; and 3, very good plantar-flexion of the foot. Inter-reliability test of these scales were done from video-recordings of walking with different anti-skid-devices on different surfaces in the experimental situation described below by two experienced physical therapists. The inter-reliability of the four observation scales were measured as the percentage of agreement between the physical therapists when observing video-recordings of all subjects in all Fig. 3. Observation of walking posture and movements in different parts of the body, heel-strike and toe-off. tests. The percentage of agreement between the physical therapists in the four observations scales were 85%, therapists. The inter-reliability of the walking safety 80%, 86% and 85% respectively. and balance scales were measured as the percentage of agreement between the physical therapists when observing video-recordings of all subjects in all tests. The 3. Material and methods used in the test of 25 percentage of agreement of the walking safety scale was anti-skid devices 86% and the corresponding agreement of the walking balance scale was 88%. Four rating scales for evalua- The rating scales for evaluating perceived safety and balance as well as the four rating scales for evaluating tion of observed walking movements were developed movements in walking described above were used in the (Fig. 3). The rating scales were developed by a physical test of 25 anti-skid devices. Another measure used was therapist, trained in movement analysis. The dimen- the subjective choice of an anti-skid device for own use. sions evaluated were: (1) walking posture and move- Each subject made a list of priority according to three ments including normal muscle function in the hip and criteria; safety, balance and appearance. These mea- knee; (2) walking posture and movements in the rest of sures were regarded as important measures in a practi- the body (head, shoulders and arms); (3) heel-strike; cal study like this, as subjects’ own priorities often and (4) toe-off. All four dimensions were evaluated by direct the everyday behaviour. Each subjects also evalu- observation scales ranging from 0 to 3. ated perceived advantages as well as disadvantages of In the first observation scale movements including each anti-skid device, after walking with each of them. normal muscle function in the hip and knee was ob- This measure was also regarded as an important subjec- served and classified according to: 0, walking with tive measure as the advantages and disadvantages may normal walking movements with adequate swaying up be used to improve the product design of anti-skid and down in knees; 1, walking with straight knees, no devices. swaying; 2, walking with straight knees, no swaying and After the development of the methods, practical tests raised shoulders; and 3, walking with straight knees, no of all 25 anti-skid devices on the Swedish market at that swaying, raised shoulders and a rigid posture. time were performed (Fig. 4). The tests were performed In the second observation scale the movement pat- in an experimental situation with five slippery surfaces tern in the rest of the body (head, shoulders and arms) (Fig. 5). Each track was 10 m long and 1 m wide. Some were observed and classified according to: 0, walking of the tracks were covered with gravel, sand, snow and with a relaxed head posture and relaxed movements in salt. trunk, shoulders and arms; 1, walking with the head Six subjects were randomly selected from the regis- and trunk in a rigid posture and small movements in tered population in Lulea˚over 55 years old and four of shoulders and arms; 2, walking in a rigid posture them wanted to participate in the study. The sequence without movements in head, trunk and shoulders, small of the devices was randomised for each subject. The movements in arms; and 3, walking in a totally rigid subjects had no earlier experience from walking with posture. the anti-skid devices. For the practical tests five differ- In the third observations scale heel-strike was ob- ent walking areas with different slippery surfaces, each served and classified according to: 0, no heel-strike, no 10 m long, were prepared: 458 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 32 (2000) 455–460

Table 1 The subjects’ (N=4) perceptions of walking safety after walking with each of 25 different anti-skid devicesa

Device number Type Gravel Sand Snow Ice Salt

1FGGFGFG B 2HFG G BFGB 3HGGBBB 4FGGBGB 5GFFGGG FG 6FGFGBBB 7WFGGG GG 8BWF FG G BN 9BFBGG FG 10 WF G FG BB G 11 HGG B BB 12 H G FG BB G 13 WF B FG BB FG 14WFFG FG B N B 15WF FG G NB FG Fig. 4. The 25 different anti-skid devices tested. 16 WFGFG FG GFG 17HG GBB B 18WFNFG FG B FG / 2 Ice with sand (180 g m ) 19 WF G G GG G Ice with gravel (4–8 mm ca 150 g/m) 20 HGG B BB Ice with 3–5 mm snow 21 F FG FG BB G Ice 22 WF FG FG BB B / 23HBGG B B Ice with salt (9 g m) 24 FFG FG BB FG To evaluate realistic walking situations in the trafﬁc 25 F FGFG BB FG environment, such as a pedestrian crossing, the walking a cycle for each walking area was divided into six parts: Walking safety was evaluated as none (N), bad (B), fairly good (FG) or good (G). The ratings of safety and balance were a total 1. Walk ‘normally’ across the whole area measure of the four subjects’ perceptions. The types of anti-skid 2. Turn around devices were heel devices (H), foot-blade devices (F) and whole-foot 3. Walk rapidly 4–5 steps devices (WF). 4. Stop 5. Walk backwards 4–5 steps 4. Results 6. Walk ‘rapidly’ across the whole area Before the test each subject had the opportunity to 4.1. Walking safety and balance walk without anti-skid device on these six parts of the Table 1 shows the subjects’ perceptions of walking experimental walking cycle so they were familiar with safety and Table 2 walking balance after walking with the situation. No other safety precautions were taken 25 different anti-skid devices. The ratings of safety and during the experiment. In the test situation each subject balance were a total measure of the four subjects’ walked with each anti-skid device on the ﬁve different perceptions. Anti-skid devices 5, 7 and 19 were per- slippery surfaces. The subjects were told to walk ac- ceived as best regarding walking safety and anti-skid cording to the instructions above. devices 7, 12 and 19 as best regarding balance.

4.2. Mo6ement analysis

When walking on snow, ice and salt one subject lacked normal walking posture and movements when walking with anti-skid devices 20 and 25. The value was 1 on the observation scale. All four subjects lacked normal heel-strike when walking on snow and ice with anti-skid devices 16 and 22 Their values were 1 on the observation scale. Three subjects lacked normal heel- strike when walking on snow and ice with anti-skid device 20. Their values were also 1 on the observation Fig. 5. The experimental set-up. scale. Three subjects also lacked normal toe-off when G. Gard, G. Lundborg / Accident Analysis and Pre6ention 32 (2000) 455–460 459 walking on snow and ice with 20, 24 and 25. They were 4.4. Subjects’ own priorities rated as 1 on the observation scale. Two subjects lacked normal movements in the rest of the body when walk- A comparison of the subjects’ highest priorities for ing with anti-skid device 20, with a rating of 1 on the own use showed that anti-skid devices 7 and 16 had the observation scale. The other subjects had normal move- highest priority regarding both safety and balance. ment patterns when walking with the different anti-skid Anti-skid numbers 4, 7 and 16 were chosen as the most devices. highly valued anti-skid device concerning appearance. When combining walking safety, walking balance and 4.3. Percei6ed ad6antages and disad6antages own usage the wholefoot devices ‘studs’ was chosen as the first and ‘sensi galoch’ as the second device. The most common advantages perceived were that the anti-skid devices were easy to put on (all anti-skid devices), gave good foothold (numbers 1–5, 7, 10, 5. Discussion 12–16), were easy to take with you (numbers 1–5, 7, 10), were easy to walk with (numbers 1–4), were small Anti-skid devices 5 ‘Tro¨nder spike’ and 7 ‘studs’ were (numbers 1, 3, 8, 9) and that they were stable (numbers perceived as best regarding walking safety and anti-skid 2 and 3). Disadvantages mentioned were problems with devices 7 ‘studs’ and 12 ‘Thulin spike’ as best regarding spikes (numbers 1–3, 10–12), that parts come loose balance. The wholefoot device ‘studs’ had a high prior- (numbers 1–2, 8–9), that they were big and clumsy ity in both walking safety and balance and had the (numbers 8, 12, 13), unsafe (numbers 9, 11, 13) and highest priority in choice for own use according to heavy (numbers 5, 10, 11). safety, balance and appearance. When observing the walking posture and movements in different parts of the body, heel strike and toe-off showed a normal pattern in all aspects when walking with the ‘studs’ anti-skid device. It was also easy to put on and gave Table 2 good foothold. The primary risk factor for slipping The subjects’ (N=4) perceptions of walking balance after walking accidents is according to Gro¨nqvist, poor grip and low a with each of 19 different anti-skid devices friction between the footwear (foot) and the underfoot Device number Type Gravel Sand Snow Ice Salt surface (pavement). As regards slipping risk, the heel- strike and the toe off appear to be the most critical 1 GF FGG GFG phases in walking. Whole foot anti-skid devices are 2BBHFGG G supposed to be the best combination of device, as they 3HGGFGBBgive the subject possibility to obtain both a normal toe 4FGGGFG G 5FG G G FG G off and a normal heel strike. Heel devices or foot blade 6 GF BFG BB devices only give one of these possibilities and influence 7GWFGGG G the subject to a restraint walking cycle, with reduced 8WF B FG B B B safety, balance and foothold. 9BFGGGB The results showed that the rating scales for describ- 10BWF FGFG GFG 11 GH BFGFG FG ing perceived safety and balance as well as the observa- 12H G G G G G tion methods for observing movements were reliable 13WF B FG B N B and could be used to describe walking safety, walking 14BWF FGBFGFG balance and walking movements when walking with 15 FGWF GGNG anti-skid devices on slippery surfaces. The measures to 16 WF G FG FG FG FG 17HGFGBB G choose an anti-skid device for own use and to list 18WF B FG FG FG FG perceived advantages and disadvantages could also be 19 WF G G G G G used in the test situation. These practical measures are 20 H G FG FG B B important, as they can show how to increase the usabil- 21FFGFG B B G ity of the anti-skid devices. It is important to make 22FGWF BFG BB 23 HG GBBB anti-skid devices as safe, comfortable and practical as 24 F FG FG B B FG possible. The anti-skid number 7 was a complete shoe 25 F FG FG B B FG with the sole covered with spikes. It was very stable and comfortable to walk with and there were no parts that a Walking balance was evaluated as none (N), bad (B), fairly good could come loose during the walking. The methods (FG) or good (G).). The ratings of safety and balance were a total measure of the four subjects’ perceptions. The types of anti-skid developed, the rating scales for perceived safety and devices were heel devices (H), foot-blade devices (F) and whole-foot balance and the four rating scales for evaluating move- devices (WF). ments were practical to use and can be recommended 460 G. Gard, G. Lundborg / Accident Analysis and Pre6ention 32 (2000) 455–460 for the future. The subjective choice of an anti-skid References device for own use where each subject made a list of priority according to safety, balance and appearance is Brocklehurst, J.C., Exton-Smith, A.N., Barber, S.M., Hunt, L.P., also a relevant measure in studies in this area as Palmer, M.K., 1978. Fracture of the femur in old age: a two-centre study of associated clinical factors and the cause of the fall. subjects’ own priorities often direct the everyday be- Age aging 7, 7–15. haviour. To evaluate perceived advantages as well as Bruce, M., Jones, C., Manning, D.P., 1986. Slip resistance on icy disadvantages of each anti-skid device, after walking surfaces of shoes, crampons and chains — a new machine. with each of them can also be recommended for further Journal of Occupational Accidents 7, 273–283. Council Directive 89/686/EEC, 21 December 1989. The approxima- use. The comparison of the subjects’ highest priorities tion of laws of the member states relating to personal protective for own use is also a practical measure of great value in equipment (PPE). Official Journal of the European Communities product development of anti-skid devices. No L 399, pp. 18–38. The experimental set-up with five slippery surfaces is Gro¨nqvist, R., 1995. A dynamic method for assessing pedestrian slip resistance. Thesis, Finnish Institute of Occupational Health, a realistic situation and the sequence of the devices was Helsinki. randomised for each subject. No specific safety precau- Gro¨nqvist, R., Ma¨kinen, H., 1997. Development of standards for tions were taken during the experiment. This may have anti-slip devices for pedestrians. In: Nielsen, R., Borg, C. (Eds.) reduced the walking pace to a slower pace the ‘walking Proceedings of the Fifth Scandinavian Symposium on Protective rapidly-phase’ compared to if safe precautions had been Clothing, (NOKOBETEF) Danish Work Environment Fund, May 5–8, Elsinore, Denmark, pp. 187–189. arranged. As a precaution in this study the subjects had Hara, F., Kawabata, T., Sakai, N., Koboayashi, I., 1991. Safety of the opportunity to walk without anti-skid devices on pedestrian walking areas in winter. In: Proceedings from ISCORD the surfaces before the experiments. Before future ex- 1991, Sapporo, Japan. periments precautions have to be discussed and if possi- Honkanen, R., 1982. The role of slippery weather in accidental falls. Journal of Occupational Accidents 4, 257–262. ble arranged. The study took place on a constructed ice Lund, J., 1984. Accidental falls at work, in the home and during area outside a laboratory. The area were slightly in- leisure activities. Journal of Occupational Accidents 6, 181–193. clined sideways (0.25%), which is approximately the Manning, D.P., Jones, C., Bruce, M., 1991. A method of ranking the same as a normal sidewalk in Sweden. The ice surface grip of industrial footwear on water wet, oily and icy surfaces. Safety Science 18, 45–60. was even. Not rough or covered with tracks from cars Merrild, U., Bak, S., 1983. An excess of pedestrian injuries in icy as it normally might be. This is representative from all conditions: a high-risk fracture group — elderly women. Accident kinds of slippery surfaces. Further studies ought to be Analysis and Prevention 15, 41–48. done on other surfaces such as surfaces made from SCB, 1987. Official report of statistics. Stockholm. hard packed snow, rough surfaces, inclined surfaces in Sjo¨gren, H., Bjo¨rnstig, U., 1989. Unintentional injuries among elderly people: incidence, causes, severity and costs. Accident Analysis the walking direction (2, 5, 8 and above 8%). No more and Prevention 21, 233–242. than 2% is supposed to be a good standard for walk- Sjo¨gren, H., Bjo¨rnstig, U., 1991. Injuries to the elderly in the traffic and bike-roads close to crossing and 5 and 8% are slope environment. Accident Analysis and Prevention 23, 77–86. standards for adopting the special requirements for Tinetti, M.E., Speechley, M., Ginter, S.F., 1988. Risk factors for falls among elderly persons living in the community. New England disabled people in Sweden. Journal of Medicine 319 (26), 1701–1707. In this study both objective and subjective methods Waller, J.A., 1978. Falls among the elderly — human and environ- were used. In our opinion it is important to use both mental factors. Accident Analysis and Prevention 10, 21–33. objective and subjective research methods in the work Wild, D., Nayak, U.S.L., Isaacs, B., 1981. How dangerous are falls in to develop European standards for anti-skid devices. old people at home? British Medical Journal 282, 266–268. Winter, D., 1984. Needs and problems of older drivers and pedestri- Anti-skid devices need to be safe and user-friendly to be ans: an exploratory study with teaching/learning implications. used. Educational Gerontology 10, 135–146.

Paper III

Submitted for publication in Accident Analysis & Prevention Experiences from evaluation of anti-slip devices

Glenn Berggård a, *, Gunvor Gard b

a Department of Civil, Mining and Environmental Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden b Department of Health sciences, Division of Health and Rehabilitation, Luleå University of Technology, SE-971 87 Luleå, Sweden * Corresponding author. Tel.: +46-920-491711; fax: +46-920-492818. E-mail address: [email protected] (G. Berggård)

Abstract Each year, thousands of pedestrians in Nordic countries are injured because of slippery pavements and roadways during the winter. Anti-slip devices on shoes are perhaps a way for individuals to prevent slipping and falling. To ensure good functionality of anti-slip devices and safe pedestrian transport during the winter, a method to test anti-slip devices was developed. Tests were performed on eight new anti-slip devices to evaluate their influence on observed walking posture and movements and subjective walking safety and balance. The method to test the devices was assessed.

The devices are divided into different functional groups: heel devices, whole foot devices, and foot blade devices. The results showed that the whole foot devices W10 and W11 had the best results concerning observed walking posture and movements, perceived walking safety and balance, and choice for personal use. These results were compared with earlier tests on 25 devices. Whole foot devices was the functional group that best supported a natural gait. Heel strike is the most important part of the gait cycle, and it is the heel part of anti-slip devices that has to be better developed to prevent slipping. Excluding the test tracks covered with gravel and sand is suggested. Expanding the observation rating scale is also suggested. Developing new anti-slip devices and methods to test anti-slip devices are needed,

Keywords: Icy surface; Pedestrians; Anti-slip devices; Assessment; Fall prevention.

1. Introduction The prevention of accidental injuries caused by slipping on icy surfaces is of great importance, especially in Nordic countries. It is expected that foot slippage will cause 43% of all falls and 16% of all accidents at work, in the home, and during leisure activities in Denmark, Finland, Norway, and Sweden (Lund, 1984). Two-thirds of these slippage events occur on pavement or other surfaces covered by ice and snow. In Finland, about 70,000 slipping accidents take place outdoors on streets, walkways and courtyards (Vuoriainen et al., 2000), of which two-thirds occur when the walking surface is covered by ice or snow (Grönqvist, 1995). The estimated total cost of slipping and falling accidents, including indirect costs, is approximately 420 million Euros per year (Vuoriainen et al., 2000). An analysis of 297 persons aged 60 and older, who were treated for injuries in the traffic environment during a one-year period, showed that falling was the main cause injury, 52% (Sjögren and Björnstig, 1991), with two-thirds of the falls involving slipping on ice and snow. Ice and snow related injuries in all categories accounted for 37% of the total cost of all elderly injuries in the traffic environment in Sweden. Special plans aimed at removing ice and snow are needed to reduce slipperiness, through the spreading of sand and salt as well as anti-slip devices (Sjögren and Björnstig, 1991). Using an appropriate anti-slip device may eliminate a pedestrian’s risk of slips and falls on ice and snow (Grönqvist and Mäkinen, 1997). In Sweden, home owners or local authorities are responsible for anti-slip management on sidewalks. Lindmark and Lundborg (1987) state that sidewalks or walkways have no standard regarding their surface condition. In a study focusing on anti-slip management, local municipalities in Sweden showed that they wanted anti-slip devices to be developed, they wanted guidelines on how to select the most preventive anti-slip devices, and they wanted to know how to use the best management techniques (Lindmark and Lundborg, 1987).

Norrman (2000) investigated winter road slipperiness and found that its development and distribution are complex due to variations in road climate. Winter road maintenance alone cannot prevent all accidents, e.g. drivers must be informed to take the necessary safety measures. Also, pedestrians should be informed about what to do to prevent slipping and falling. Having information about road and sidewalk surface conditions, choosing the correct winter footwear, using an appropriate anti-slip device, or a combination of the aforementioned are important pedestrian actions to prevent slipping or falling on ice and snow. A weather condition and pavement condition model was developed and is now used by the Finnish Meteorological Institute to provide a winter weather service to pedestrians. By giving warnings of slippery conditions, the number of slipping accidents should be reduced, and therefore perhaps improve the safety of pedestrians during winter (Aschan et al, 2005). High risk periods are within 24 hours after a light snowfall on pure ice with a temperature of only a few degrees Celsius below freezing (Nilsson, 1986).

Risk factors relating to slips and falls may be extrinsic (environmental factors), intrinsic (human factors), or mixed (system factors) (Grönqvist, 1995). The primary risk factor for slipping accidents, according to Grönqvist, is poor grip and low friction between footwear (foot) and underfoot surface (pavement) (Grönqvist and Hirvonen, 1995). Regarding the risk of slipping, the heel-strike and toe-off appear to be the most critical phases in walking. Human factors such as age and gender can be risk factors for slips and falls (Kioski et al., 1996). Women participate more often in slipping and falling accidents than men in the age group 80 years and younger (Tinetti and Speecheley, 1989; O’Loughlin et al, 1993), since women often have a higher activity level than men and are exposed to increased working environment risks (O’Loughlin et al., 1993). Studies in Sweden also show that women, especially in the age group 45 – 74 years old, are involved to a greater extent in slip accidents on snow and ice than men (Nordin, 2003). One explanation seems to be that women walk more often than men (Nordin, 2003). Living alone might also be another risk factor for these accidents (Jarnlo and Thorngren, 1993).

Walking ability and walking patterns can be seen as risk factors for slips and falls among both men and women. Risky walking patterns and situations have been identified, specifically a tripping walking pattern, rough and uneven surfaces, and short footsteps (Tinetti et al., 1986, 1988, 1996). In analysing walking patterns and walking problems, various aspects can be observed: heel-strike, toe-off, length of steps, height of steps, symmetry of steps, rhythm of steps, rotation of different body parts, and deviations in walking patterns (Tinetti, 1986). A study of healthy individuals showed no significant differences between men/women and young/old in walking ability and walking patterns on icy surfaces (Gard and Berggård, 2006).

Quantitatively, the coefficient of friction (COF) between the interacting surfaces usually determines slip resistance. Therefore, the frictional properties of shoe heels and soles play an important role in preventing slips and falls. However, Grönqvist and Hirvonen (1995) noted a

2 considerable lack of knowledge about the slipperiness of footwear soles on icy surfaces. Only three earlier studies concerning devices for assessing footwear friction on ice and the anti-slip properties of different types of winter shoes on icy surfaces have been done (Manning et al., 1985; Manning et al., 1991; Bruce et al., 1986). More recently, Gao (2001, 2004) also identified the risk of slipping and falling on ice and snow using different winter footwear. The footwear test included winter footwear, professional footwear, safety footwear, and footwear considered to be slip resistant by manufacturers, though none provided adequate protection against slips and falls on melting ice. Therefore, Gao suggested additional measures to reduce slip and fall risk on melting ice (2004). A pilot study conducted in 2005, involving 95 participants, showed that the use of an anti-slip device can be valuable in preventing slip accidents (Juntunen et al, 2006).

Studies have assessed the anti-slip properties of different types of winter shoes on wet and dry icy surfaces (Grönqvist, 1995). Comparative studies of friction measurement devices show that few are capable of closely simulating the force and motion of the human gait (Grönqvist, 1995). The effect of winter footwear sole abrasion on the coefficient of friction on melting and hard ice has also been studied (Gao et al., 2003), using the same test area and walking cycle as in our studies. The correlation between subjective ratings of tendency to slip, objective COF measurement and direct observation showed a significant correlation between subjects ratings and COF (r= 0.900, p = 0.037 <0.05), ratings and observation (r = -1.000, p = 0.000 < 0.01), and COF and observation (r = -0.900, p = 0.037 < 0.05) (Gao, 2001). A pilot study (Berggård et al, 2009) indicates good correlation between perceived ranking and measured friction of 3 different anti-slip devices and 107 subjects. The heel device shoved the highest DCOF (Dynamic Coefficient of Friction) and was chosen no 1.

Table 1. The dynamic coefficient of friction (DCOF) and standard deviation (SD) values on smooth ice for tested anti-slip devices. (from Bergård et al, 2009) Type of device DCOF SD H7 0.36 0.02 F11 0.30 0.06 W11 0.26 0.02

Some evaluation methods used when testing anti-slip devices were developed and described in Gard and Lundborg (2001). Rating scales to evaluate walking safety and walking balance were also developed with a method to observe walking posture and movements. The inter- rater reliability of the walking safety and walking balance scales were studied and found acceptable (Gard and Lundborg, 2000 and 2001). Four rating scales to evaluate observed walking were also developed with acceptable inter-rater reliability (Gard and Lundborg, 2001). When analysing the results, it was noticed that it is efficient to divide the anti-slip devices in different functional groups – heel devices, whole foot devices, and foot blade devices (See Figure 1). Comparing the similarities and differences within and between these various groups might deepen knowledge about the use and benefits of anti-slip devices.

Gard and Lundborg (2000) also tested 25 anti-slip devices from the Swedish market on different slippery surfaces. The anti-slip devices were described according to the subjects' perceptions of walking safety, walking balance, and their personal reasons for choosing an anti-slip device. Also, an expert physical therapist analysed their postures and walking movements. By identifying risk factors for outdoor slips and falls during the winter, appropriate methods to prevent slipping and falling can be developed, e.g. suitable anti-slip devices and methods to evaluate anti-slip devices.

In these Laboratory tests, called A and B, the subjects were randomly selected from the inhabitants of one residential area in Luleå. In the first test, Laboratory test A, 19 anti-slip devices were tested by 4 subjects (Gard and Lundborg, 2000); in the second test, Laboratory test B, the same subjects tested 6 new anti-slip devices as well as 2 previously tested (Gard and Lundborg, 2001) of the same types that were to be tested. The number of devices were randomised to remove any relation between the number of devices and their characteristics.

In the tests, the subjects walked on 5 different walking surfaces with varying slipperinesses, each 10 meters long (Gard and Lundborg, 2000, 2001). The length chosen was an average pedestrian crossing. A small inclination (2.5%), as found sideways on sidewalks, was also used on the walking areas. The area consisted of separate tracks: ice covered with sand (180 g/m2), ice covered with gravel (4 – 8 mm approx. 150 g/m2), ice covered with 3 – 5 mm of snow, ice, and ice covered with salt (9 g/m2). In the tests, each subject first walked without any anti-slip device, followed by with each of the anti-slip devices on the five different slippery surfaces. The subjects were video recorded. After walking with each device, each subject rated their perceived exertion, walking safety and walking balance, and time to put on and take off each anti-slip device (Gard and Lundborg, 2000 and 2001). After walking with all the tested devices, each selected one anti-slip device for personal use (Gard and Lundborg, 2000 and 2001).

Below the results of the earlier tests are presented. The devices are consecutive numbered and referred to by their principal type: Foot blade devices as F1, F2 ,…, Heel devices as H1, H2, … and Whole foot devices as W1, W2, …. .

In the first Laboratory test, test A, anti-slip device W1 had the highest rating among half the subjects in walking safety and W7 had a high rating in walking safety. W1 and W7 also had the highest rating regarding balance. There was a tendency to choose anti-slip devices F2, W1, W7 and W9 for personal use. When combining walking safety, walking balance, and the test subject’s subjective reasons for personal use, W1 was rated first and W7 second. Both devices were whole foot devices (Gard and Lundborg, 2000). Because W9 was shoes with built-in activated/deactivated devices and W1 wellingtons with non-detachable studs, they were not choosen for comparisons in later tests with detachable devices.

In the second Laboratory test, test B, anti-slip devices W7 and W10 had the highest rating in walking safety, balance, and choice for personal use amongst the subjects (Gard and Lundborg, 2000). The arguments for choosing W7 were perfect safety and balance, with anti- slip device W7 offering good safety. It was suggested that W10 should be modified to be less clumsy and fit the shoe better. Both were detachable whole foot devices.

Further tests and improvements of the test methods and safety and ergonomic aspects of anti- slip devices were found to be needed.

Figure 1. Different functional groups of anti-slip devices.

2. Aim

The aim of this study is: - to identify the design properties of anti-slip devices for pedestrians that makes them safer and to influence future safer design of anti-slip devices and -to assess the methods use in testing anti-slip devices

3. Method

In this study, eight new anti-slip devices were tested and compared with the results from earlier Laboratory test of anti-slip devices. In this study, the same experimental test situation as in earlier tests was employed. In the first part of this study, Laboratory test C, four new devices were evaluated by the same four subjects as in earlier studies (Gard and Lundborg, 2000). In the second part of the study, Laboratory test D, another four new anti-slip devices were tested by two old and two new subjects. The subjects were experienced year-round pedestrians. They were not familiar with any specific anti-slip device. The evaluation methods were the same as earlier described (Gard and Lundborg, 2001). All tests, A-D, were performed during a 4-year period, and when new products entered the market, either as upgrades of earlier designs, improved materials, or new products or prototypes on the Swedish market.

For comparison purposes with previous results, one or two previously tested devices were chosen in each new test. In test B two new detachable heel devices were tested with three footblade devices and one whole foot device. To identify the differences of the various devices two old devices were also tested in B, i.e. H3, the best detachable heel device from test A, and W7, the best detachable whole foot device from test A. In test C two new footblade devices and two new whole foot devices were tested, along with the best detachable footblade device from test A, F2, and the best detachable whole foot device from test B, W10. In test D one new footblade device, one heel device and two new whole foot devices were tested, together with the best detachable whole foot device from test C, W11.

Table 2 a-c shows the characteristics of the 8 new tested and 25 earlier tested anti-slip devices.

5 Table 2a. Foot blade anti-slip devices in this study as well as previously tested and their specific characteristics

Device no. Acti- Name Construction Friction per Fastening Comments vation material shoe by * (no. of edges)

Tested in this study

F9 d Rud Polymer, steel Chain welding Elastic bands Quickstep points (appr. 10) F10 f Conti- Sole pattern Mounted by contact shoemaker F11 d Dubby Polymer, steel Studs (5) Elastic bands

Previously tested (Gard and Lundborg, 2000)

F1 d Halkej Polymer, steel Studs (3) Strapped over No strap to the the foot blade heel to prevent from slipping of. 3 edges towards the sole to prevent from sliding. F2 d Yngsjö- Polymer, steel Steel edges (5 Elastic bands 4 edges towards spike larger, 2 the sole to prevent smaller) from sliding F3 d Trönder Polymer, steel Steel edges (4) Strapped over 4 edges towards the foot blade. the sole to prevent Elastic bands to from sliding the heel F4 d Conti Polymer, steel Studs (4) Elastic flat Spiky punched/cut out bands F5 d Ö-viks Polymer ring, Screw pin (3) Elastic polymer 3 edges towards steel ring the sole to prevent from sliding F6 d Sport Leather, steel Steel edges Leather strap To be used with a buckle kick-sled F7 d Sandy Polymer, Ceramics Elastic bands ceramics (sandpaper) F8 d Sandy Polymer, Studs (5) + Elastic bands with studs ceramics, steel ceramics (sandpaper) *a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoe maker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe.

6 Table 2b. Heel anti-slip devices in this study as well as previously tested and their specific characteristics

Device no. Acti- Name Construction Friction per Fastening Comments vation material shoe by * (no. of edges)

Tested in this study

H8 a Sure foot Steel Steel edges (4) Mounted by shoemaker

Previously tested (Gard and Lundborg, 2000)

H1 a Cats Steel Steel wire tip Mounted by (2) shoemaker H2 a Rewa Steel Steel edges (2) Mounted by shoemaker H3 d Eissporn Polymer, steel Steel edges Strapped with (36) buckle H4 d Thulin Polymer, steel Steel edges Strapped with 2 edges towards (18) buckle the sole to prevent from sliding H5 a Panther Steel Steel (2) Mounted by the Snow boots with manufacturer pre-mounted heel devices H6 d Frost Leather, Steel Steel edges Leather strap buckle H7 d Instant Special rubber Studs (4) Velcro© Reflex in the back stop/Icey mix with high fastening friction, steel, polymer *a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoe maker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe.

7 Table 2c. Whole foot anti-slip devices in this study as well as previously tested and their specific characteristics

Device no. Acti- Name Construction Friction per Fastening Comments vatio material shoe by n* (no. of edges)

Tested in this study

W11 d Bergsteiger Polymer, steel Chain welding Elastic bands points (appr. 20) W12 d Universal Polymer, steel Screw pin (5- Bootlace Prototype Kit 20) assembled by the user W13 f All stop Steel Steel cups (9) Mounted by user Prototype (glue and screws) W14 a APA Shoe Polymer, steel Studs (8) Velcro© spikes fastening

Previously tested (Gard and Lundborg, 2000)

W1 f Studs Steel Studs (13) Mounted with a Studs used for delivered special predrilled tool wellingtons W2 f Glistop Chemicals: Uneven Spread under the Health risk when Prepolymer surface sole. Dry 24 applying MDI, Xylen hours. W3 d Metal Steel Perforated Bent metal Stiff, heavy metal rail (25 hole edges) W4 d Wish Polymer, steel Steel edges on Velcro© Stiff metal rail (22 fastening steel edges) W5 d Ice spike Polymer, steel Steel edges (12 Buckle (the grip Two parts. The + 24) handle work in foot blade device the opposite loosens when direction for the attaching foot blade devices and does not tighten the strap on the device) W6 f Extra Rubber/polym Sole pattern Mounted by er shoemaker W7 d Sensi Polymer, steel Spikes (14) Galosh Overshoe

W8 d Ice gripper Polymer, Steel Steel edges Velcro© (32) fastening W9 a Beaver Steel Steel edges (4 Mounted by the Snow boot with + 4) manufacturer both pre mounted heel and foot blade device W10 d Icer’s/Stabil SBR rubber, Replaceable Velcro© Heavy icer steel studs (17) fastening *a = activated/de-activated devices built onto the shoe by the manufacturer or afterwards by a shoe maker, d = detachable anti-slip devices, f = fixed anti-slip devices built onto the shoe. ** device no. 29 is a kit that can be combined and used as a foot blade device, a heel device or as a combined whole foot device.

8 4. Results

4.1 Assessment of anti-slip properties of eight new anti-slip devices

An adequate walking pattern including normal muscle function in the hip and knee was observed for all subjects when walking with all anti-slip devices on gravel and sand. All except one subject also displayed an adequate walking pattern on ice and salt. Three foot blade devices, F2 (in the second test), F9 and F10, two whole foot devices, W10 and W11 (in the first test of the device), and one combined device, W12, showed adequate walking postures and walking patterns for all subjects on all surfaces. Adequate heel strike was observed for all subjects on all surfaces when they walked with W10 (in the second test), W11, W14, and F2 (a foot blade device is not expected to have perfect heel strike because it is only located under the forefoot). The same anti-slip devices, i.e. W10 (in the second test), W11 (in both tests), W14, and F2 (second test) foot blade device, showed acceptable toe-off on all surfaces. An adequate and relaxed body posture in the head, shoulders, and arms was observed in all subjects on all surfaces when walking with three foot blade devices, F2, F9 and F10, two whole foot devices, W10 (second test of the device) and W11 (first test of the device), and one combined device, W12.

In summary, W10 (second test for the device), W11 (first test for the device), and F2 (second test) permitted walking with an adequate walking posture and movement, including normal muscle function in the hip and knee, heel strike, toe-off, and movement patterns in the rest of the body for all subjects on all surfaces. One whole foot device, W14, showed acceptable heel strike and toe-off on all surfaces for all subjects. Two foot blade devices, F9 and F10, and one combined device, W12, permitted acceptable walking posture and movement, including normal muscle function in the hip and knee and movement patterns in the rest of the body for all subjects on all surfaces.

Table 3 shows the subjects’ perceptions of walking safety after walking with each anti-slip device. All devices except F11 were perceived as having good or very good walking safety on gravel and sand. The foot-blade and whole foot devices were perceived as having good walking safety on salt.

9 Table 3. Perceived walking safety with different anti-slip devices. The results from the second test some devices participated in is shown in italic. (The rating scale is: ++ very good, + good, +/- not good or bad, - bad, -- very bad).

Anti-slip device Type Surface Gravel Sand Snow Ice Salt Tested only in this study F11 F ------F9 F + ++ -- - + F10 F + ++ -- +/- ++ H8 H + ++ - - - W12 H/WF/F + ++ +/- +/- ++ W13 WF + + -- - - W14 WF ++ ++ + + + Double tested W11 WF + ++ +/- + + W11 WF ++ ++ + + + F2 F ++ ++ + +/- + F2 F ++ ++ -- - ++ H3 H ++ ++ +/- +/- +/- H3 H + ++ - +/- + W7 WF ++ + + + ++ W7 WF ++ ++ +/- + ++ W10 WF ++ ++ + ++ ++ W10 WF + ++ +/- ++ +

Anti-slip devices W7 (first test of the device), W10, W11(second test of the device), and W14 showed good or very good perceived safety for all surfaces. All were whole foot devices.

Table 4 shows the subjects perceived balance after walking with each anti-slip device.

Table 4. Perceived balance with different anti-slip devices. The results from the second test some devices participated in is shown in italic. (The rating scale is: ++ very good, + good, +/- not good or bad, - bad, -- very bad). Anti-slip device Type Surface Gravel Sand Snow Ice Salt Tested only in this study F11 F ------F9 F ++ ++ -- - + F10 F ++ ++ -- - + H8 H + + - - - W12 H/WF/F ++ ++ +/- +/- ++ W13 WF + ++ - - - W14 WF ++ ++ - - - Double tested W11 WF ++ ++ +/- +/- + W11 WF ++ ++ + + + F2 F ++ ++ + ++ ++ F2 F ++ ++ - +/- ++ H3 H ++ + + - + H3 H + ++ -- -- +/- W7 WF ++ + + + + W7 WF ++ ++ ++ ++ ++ W10 WF ++ ++ ++ ++ ++ W10 WF ++ ++ ++ ++ ++

Anti-slip devices W7, W10, and W11 (second test of the device) showed good or very good perceived balance for all surfaces. All were whole foot devices.

Whole foot devices were rated first, W11, and second, W10, as chosen for personal use by the subjects in the first part of the study, test C. In the second part, test D, the whole foot device W11 was still chosen first, but the fixed heel device H8 was chosen second.

4.2 Assessments of the methods and surfaces used in relation to earlier tests.

Assessment is based on the eight new tested devices and the devices tested twice. The differences in perception between different surfaces for the tested devices (N=17) shows the largest differences in perception of walking safety between snow – gravel for 17 of the devices and snow – sand for 16 of the tested devices. The difference is nearly as large in perception of balance between snow – gravel, for 14 tested devices, and snow – sand, for 12 devices.

Table 5. Differences in perception of balance and walking safety for anti-slip devices between different surfaces. Perceived No. of differences in perception between different surfaces (N=17) Snow-ice Snow-salt Snow-sand Snow-gravel Ice–salt Gravel-sand Balance 5 7 12 14 7 4 Walking safety 10 12 16 17 9 8 Total 12 19 28 31 16 12

The subjects’ perception of walking safety and balance does not show any large variation between the devices on gravel and sand. The subjects perception of walking safety on gravel is better than on salt for all except two of the anti-slip devices. The subjects perception of walking safety on sand is better than on salt for all except one of the anti-slip devices. This indicates that icy surfaces covered with gravel and sand can be excluded in future tests.

Variations in perception for both walking safety and balance between the different devices are largest on snow and ice, indicating the possibility to record the differences in performance among different anti-slip devices. Therefore, walking on snow and ice is essential in assessing the performance of anti-slip devices. By using surfaces with snow on ice, pure ice and salt on ice, deficiences among the tested devices can be distinguised.

A combination of results from the observations of heel strike and the perceptions of walking safety on snow and ice is presented in Figures 2 and 3.

The perception of walking safety compared with the number of observed acceptable heel strikes on snow is shown in Figure 2 for both the devices tested twice and those tested in this study. The dispersion of the results from the observation and the perception does not imply the possibility to exclude any of the methods used.

11 F22 W102 W14 4

W111 W112

3 H32 Device type:

2 H8 Foot blade

F9 F10

1 F11 W12 W13 Whole foot

0 W72 W101 Heel

----/++++

Figure 2. Percieved walking safety combined with observations of acceptable heel strike on snow (The perceived rating scale is: ++ very good, + good, +/- not good or bad, - bad, -- very bad. The figures 0-4 indicates the number of subject with observed acceptable heel strike)

The perception of walking safety compared with the number of observed acceptable heel strikes on ice is shown in Figure 3 for the devices tested twice and those tested in this study.

The dispersion of the number of acceptable heel strikes on ice is similar to that on snow, but the recorded perception of walking safety on ice has increased slightly for most of the devices compared to when walking on snow. This indicates that walking on snow covered ice is perceived as the most difficult task to perform. Snow covered ice surfaces, as well as pure ice surfaces, should therefore always be included as testing surfaces for anti-slip devices.

12 W111 4 F22 W14 W102 W112

3 H32 Device type:

2 H8 Foot blade

F11

1 W13 F9 W12 F10 Whole foot

0 W72 W101 Heel

----/++++

Figure 3. Percieved walking safety combined with observations of acceptable heel strike on ice. (The perceived rating scale is: ++ very good, + good, +/- not good or bad, - bad, -- very bad. The figures 0-4 indicates the number of subject with observed acceptable heel strike)

5. Discussion

In this study the whole foot devices W10 and W11 had the best results concerning observed walking posture and movements, perceived walking safety and balance, and choice for personal use. This result is supported by earlier published tests (Gard and Lundborg, 2000), which showed that these detachable whole foot devices permitted good walking safety and balance, as well as adequate walking postures and movements on all surfaces. W11 was also the device from earlier studies with the highest rating for personal use (Gard and Lundborg, 2000). When combining the observations and subjective ratings, W11 was chosen because it permitted a normal gait and good walking safety and balance on all surfaces.

The development of new anti-slip devices combining various qualities is needed. However, users sometimes seem to consider aspects other than perceived safety and balance when choosing an anti-slip device of their own. Mainly, they prefer devices that are easily portable and easy to put on. An anti-slip device is considered as something you would not think about using. An individual with problems walking does not want to use equipment that reveals their problems or interferes with their dress or choices of footwear. This study showed that the whole foot devices W10 and W11 had the best results concerning observed walking posture and movements, perceived walking safety and balance, and choice for personal use. We recommend these detachable whole foot devices. Future development of whole foot devices should consider the best characteristics of foot blade devices and heel devices. The heel strike is the most important part of the gait in preventing slips and falls (Redfern et al, 2001). We believe that the development of attractive and well functioning heel and whole foot devices are vital in preventing slips and falls, as well as recommend that the best foot blade device should be improved in toe-off and the best heel device should be improved in heel strike.

Figure 4. Location of studs/points on two types of heel devices. To the left with defencies in heel strike and to the right with perfect performance of heel strike.

Figure 5. Location of studs/points on two types of whole foot device. To the left across the sole and to the right closer to the perimeter.

The location of the studs/points on the device probably influences user performance. The heel device to the left (Figure 4) is a modern device designed with the studs located underneath the heel with the subject failing to perform adequate heel strike, whereas the device to the right has the anti-slip points located along the perimeter, thereby allowing the subjects to perform perfect heel strike.

Even though the whole foot device to the left (Figure 5) does not have any anti-slip points at the end or front of the device, it still performs well due to the number of anti-slip points in contact with the slippery surface. The ideal location of the studs are along the perimeter of the shoe, as shown at the right of the figure.

Primarily, there is a need for better and handier whole foot devices that permit a normal gait. The devices should be flexible and lightweight, since devices that are too stiff give an unnatural gait with a flat approach of the shoe to the ground. Hence, acceptable heel strike or toe-off is not obtained. By displacing the centre of gravity the foot is forced forward into an unnatural and stressful position. The gait is incomplete and proper toe-off is difficult to obtain. Improved muscle strength in the knee and hip muscles is required when using a very heavy device. Heel devices allow for satisfactory mobility, when the swing of the step is increased in length. To develop attractive devices, advantages from the best devices in each functional group should be considered in the development of new anti-slip devices.

It is important to have both subjective ratings and observational data in these kinds of studies. In the ratings in this study, perceived safety was defined as a stable posture where the body’s centre of mass is within the base of support (Holbein and Chaffin, 1997), i.e. focus on posture. Walking balance was defined as the dynamics of the body posture to prevent falling (Winter, 1995), i.e. focus on balance. This includes the subjects’ perception of tendency to slip which therefore indirectly indicates the subjects rating of the COF. Both safety and balance were rated on a 4-point rating scale (Gard and Lundborg, 2000). Both of these subjective aspects should be covered in any future studies of this kind. The observations were

14 done from videorecordings focusing on body posture and movements. The 4-point evaluation scale used should be developed to greatly differentiate between small differences in gait- patterns. The methods for gait analysis are primarily developed for use in indoor conditions. Our observations show that when walking on slippery outdoor surfaces, an adopted gait is used. The step length is decreased. The swing of the leg is restricted. The roll over phase is excluded and replaced by a flat approach of the foot to the ground and a flat lift of the foot from the ground. The subjects seemed to adjust their gait pattern to the type of anti-slip device used. The heel device supports a natural heel strike, the foot blade device supports a natural toe-off, and the whole foot device supports a natural gait with heel strike, roll over and toe- off. Studies by Cham and Redfern (2002) also show that subjects adopt their gait to “potentially” slippery surfaces. Another study (Fong et al, 2008) suggests that greater toe grip and gentler heel strike are strategies to adopt to slippery surfaces. Hence, due to the subjects’ flatter gate pattern in our tests, the heel strike might have been more difficult to differentiate in the analysis and not as critically as in ordinary walking. Methods to describe and analyse outdoor walking should therefore be further developed. There are two basic foot movements in a gait, i.e. dorsiflexion and plantar flexion, when the ankle joint acts as a fulcrum. Therefore, the closer the centre of gravity (COG) of the footwear and the attached anti-slip device, the easier it is to walk. The COG for anti-slip devices together with the footwear used should be considered in future tests.

The walking capacity, heel strike, toe off, and walking posture and movements were acceptable for all subjects with all devices on gravel and sand. For all other surfaces there was a variation in acceptable performances of the number of subjects for different anti-slip devices. This indicates that walking on gravel and sand can be excluded in the test procedure. The variations in perception both for walking safety and balance between the different devices is largest on snow and ice. By using surfaces with snow, ice and salt the deficiences between the tested devices can be distinguised.

Measuring the subjects’ attitudes to each anti-slip device, such as handling and usage, design, and ease of carrying, is needed. Developing a more positive attitude to using an anti-slip device is important to prevent slips and falls outdoors. Qualitative studies concerning more in-depth experienced advantages and disadvantages after using an anti-slip device may be valuable. Also, quantitative studies of how walking with whole foot and heel devices physiologically and biomechanically influence the gait pattern, for example step length, walking pace, muscle coordination, heel strike and total postural control. Quantitative methods, such as step counter, accelerometer and EMG, may be used in these kinds of studies.

The method and required safety criteria for coefficients of friction should be assessed based on the study performed with the subjects, and the test method should be validated using walking tests with different anti-slip devices on icy surfaces. The devices should be described according to the subjects' perception of walking safety and walking balance, and include the test subject’s personal reasons for choosing an anti-slip device, as in Gard and Lundborg (2001). Comparative studies of friction measurement devices show that several devices are capable of closely simulating the force and motion of the human gait (Grönqvist, 1995). Hansson et al. (1999) developed a method to estimate the probability of slips and falls based on measurements of available and required friction. Slips with recoveries and slips resulting in falls were recorded and categorized using a force plate and high-speed video camera. The results showed that the number of slip and fall events increased as the difference between the required and measured coefficient of friction increased. These types of measurements and

15 analyses could assist in the design of safer environments (Hansson et al., 1999). A study assessing floor slipperiness also indicates that both objective and subjective measures of slipperiness are important in field studies (Chang et al., 2004). Average friction coefficient and subjective perceptions may agree well and possibly be good indicators of slipperiness (Chang et al., 2004). Postures and movements during walking should also be analysed. The ease of use, unhindered mobility of the foot, weight of the device, compatibility with other leg protectors and safety footwear have to be assessed.

Future studies should involve walking on other surfaces, such as inclined surfaces, rough surfaces, and surfaces of hard packed snow. The different walking speeds of different age groups should be considered, since walking at one’s own pace is important in walking safely. Also, training people with different walking problems to walk safely with or without walking aides on different surfaces is important. Further studies on the usability of whole foot and heel devices may be needed to study the effectiveness, efficiency and satisfaction with which specific user groups achieve their specific goals in walking outdoors on different surfaces during winter. If an increased usability of the best anti-slip devices could be obtained, injuries may be prevented and be cost-effective for society.

One model, F7, was not perceived to function properly in our earlier studies (Gard and Lundborg, 2000), but was later approved by the notified body performing the tests according to the Counsel directive. The establishment of a European standard for special footwear and attachments containing spikes or studs for professional use has been suggested. This is insufficient. A standard should be established for special footwear and attachments containing spikes or studs for private use as well (Lundborg, 2001).

6. Conclusion

The whole foot devices W10 and W11 had the best results concerning observed walking posture and movements, perceived walking safety and balance and choice for personal use. This result is supported by earlier published tests. Whole foot devices should be further developed, as well as the method to test anti-slip devices, for instance surfaces with gravel and sand can be excluded.

Acknowledgement

The development of the method was financed by the COLDTECH foundation. The practical tests were financed by the Swedish National Board for Consumer Policies.

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Paper IV Anti-slip devices - a need for a standardised test method

Glenn Lundborg Department of Environmental Engineering Luleå University of Technology SE-971 87 Luleå, SWEDEN Email: [email protected]

1. INTRODUCTION

The prevention of accidental injuries caused by slipping on icy surfaces is a neglected area of public concern in many countries . More then 100 000 pedestrians in the Nordic countries are expected to have medical consultation because of slippery weather conditions every winter. The injury rate is higher among the elderly. Similar observations have been made in other countries with slippery weather conditions (Hara et al, 1991). Special schemes are needed to remove snow and ice and reducing the slipperiness by gritting and salting (Sjögren and Björnstig, 1991). The local authorities responsible for snow clearance and gritting are reducing their cost and also therefore reducing their work with anti-slip treatment. Using an appropriate anti-slip device adapted to these conditions might prevent from slipping and falling (Björnstig et al, 1997). Risk factors for slips and falls may be extrinsic (environmental factors) or intrinsic (human factors) or mixed (system factors) (Grönqvist, 1995). Individual factors as age and gender can be risk factors for slips and falls. Walking ability and walking patterns can be seen as risk factors for slips and falls among both men and women. The primary risk factor for slipping accidents is, according to Grönqvist, poor grip and low friction between the footwear (foot) and the underfoot surface (pavement). As regards slipping risk, the heel-strike and the toe off appear to be the most critical phases in walking. The heel-strike causes a forward slip on the leading foot, whereas the toe-off causes a backward slip on the sole forepart, which can be counteracted by stepping forwards with the leading foot. The forward slip starting at heel-strike, would very likely result in a dangerous fall backwards, due to the fact that the forward momentum of the body maintains the body weight on the slipping foot and allows the sliding movement to continue into a fall. The prevention of slipping requires that one considers risky situations where there is very little friction between the shoe and the surface (Leclercq, 1999).

2. MEASURING METHODS

Measuring methods have to consider the different risk factors for slipping and falling with regard to both environmental factors and human factors. Below some suggested methods are presented.

2.1 Slip resistance

Studies have been done on assessing of the anti-slip properties of different types of winter shoes, on wet and on dry icy surfaces (Grönqvist, 1995). Slip resistance has been assessed by objective friction measurements and by subjective methods (paired comparisons). A friction measurement apparatus and a method for assessing slip resistance of the heels and soles of footwear on icy surfaces have been developed for laboratory use (Grönqvist 1995). Comparative studies of friction measurement devices show that few devices are capable of simulating closely the force and motion in human gait (Grönqvist, 1995).

2.2 Measurement of sudden movements

A method has been developed by Hirvonen et al (1994) for monitoring the occurrence of sudden movements in situations like slipping or tripping where there might be harmful loading of the spine. The method is based on measurements of trunk acceleration. Slipping and tripping involve rapid motions resulting from the person’s effort to regain balance. These movements can be detected by measuring the acceleration of the human body. The acceleration values are higher in sudden movements, like slipping and tripping, than in normal movements, like walking. By attenuating the normal movement signals by low-pass filtering, it is possible to discriminate signals caused by sudden movements. The portable equipment consisted of a small acceleration transducer, a pre-amplifier and a pocket computer (PSION organiser). (Hirvonen et al., 1994). Other methods for measuring acceleration have later been developed, such as a trunk accelerometer, as a method for assessing balance under various task and environmental constraints. (Moe-Nilsen, 1999). A later study on transitional friction measurement and pedestrian slip resistance (Grönqvist, 1997) shows that there should be further research on the relationship between static, transitional and steady-state kinetic friction. All three should be dealt with when considering slip resistance test methods and specifications for floorings and footwear.

2.3 Methods to describe functional problems in walking on slippery surfaces during winter.

Methods to describe functional problems in walking on different slippery surfaces outdoor during winter have been developed. More than 25 different anti-slip devices have, during several years, been tested using these methods (Gard, G. and Lundborg, G., 2000 and Gard, G. and Lundborg, G. 2001). 4-10 subjects have been participating in these tests each time. The subjects were video recorded during their walk on different icy surfaces using different anti-slip devices. The movement patterns were analysed by an experienced physical therapist. The subjects’ own perceived walking security and balance, perceived advantages and disadvantages for each of the devices was recorded. Also the subjects’ own priorities among the different tested anti-slip devices were recorded. Rating scales for perceived walking safety and walking balance were developed and tested for reliability. Four rating scales for evaluation of observed walking movements were developed: walking posture and movements including normal muscle function in hip and knee, walking posture and movements in the rest of the body, heel-strike and toe-off. The tests of the anti-slip devices on the Swedish market show unsatisfactory results for several of them that later has been approved by a notified body according to the Council directive (89/686/EEC).

2.4 Questionnaires

Questionnaires have been used to study the risk of accidents. A study of the role of sudden movements has been made (Hirvonen et al, 1996). The subjects were asked to rate their subjective risk of accident while walking on slippery surfaces compared to three other situations. A study of workers perceived sense of slip during task performance on slippery surfaces has also been made (Chiou et al, 2000). It indicates that subjects were able to perceive the likely slips due to the change in job-task and surface slipperiness. The Perceived Sense of Slip (PSOS) scale used is easy to use and reproducible. It also provides a simple way to evaluate the potential slip hazard in the workplace.

3. A NEED FOR A STANDARD

Currently there are no commonly accepted standards for testing anti-slip devices. The manufacturers, or their authorised representatives, are in Europe responsible for the fulfilment of the essential health and safety requirements stipulated in the Council directive 89/686/EEC. A notified body has to make the EC type-examination and the conformity assessment procedure according to Council Decision 90/683/EEC. The approvals also state complementary information for the future user that has to be enclosed with the anti-slip device put up for sale. These tests are today carried out by objective methods such as friction measurement at a notified body, The Finnish Institute of Occupational Health (FIOH) . The WG3-slip resistance expert group of CEN/TC161 (TC161 = technical committee of foot and leg protectors) has in March 2001 suggested that TC should have a new work item for special purpose footwear and attachments containing spikes and studs (CEN/TC161/WG, 2001). The resolution is intended to support the establishment of a standard for professional use. In order to develop CEN standards for measuring slip resistance properties of safety, protective and occupational footwear for professional use, a study was carried out involving six laboratories (de Lange and Grönkvist, 1997). Both biomechanical studies involving human subjects and mechanical slip test methods were used. A standard should make a distinction between requirements for private and for professional use and be performance oriented (Grönqvist and Mäkinen, 1997). Beside the ergonomic aspects of the anti-slip device, other aspects should also be included, such as: ease of use, unhindered mobility of the foot, weight of the device, compatibility with other leg protectors and safety footwear, perceived walking security, perceived balance, perceived advantages and disadvantages.

4. DISCUSSION

As shown above, there were results from the tests by Gard and Lundborg where several anti-skid devices that showed unsatisfactory results later have been approved according to the Council directive. There are suggestions for the establishment of an European standard for special footwear and attachments containing spikes or studs for professional use. This is not sufficient. A standard should also be established for special footwear and attachments containing spikes or studs for private use as well. For these tests both objective and subjective methods have to be utilised to avoid the marketing of anti-slip devices unsuitable for the user and their purpose of prevention from slipping and falling. There is a need to develop European, and global, standards for testing anti-slip devices which includes different methods. Comparative tests have to be made to evaluate which methods that should be used in such a standard. The standard should have a human centred approach.

REFERENCES

Björnstig, U., Björnstig, J. And Dahlgren, A., 1997, Slipping on ice and snow - elderly women and young men are typical victims. Accident Analysis & Prevention, 29 (2), Pp 211-215.

CEN/TC161/WG3 Doc. N March 2001. Resolution of WG3 arising from meeting held 26th March 2001 concerning: ENV 13287 - Safety, Protective & Occupational Footwear for Professional Use - Slip Resistance.

Chiou, S., Bhattacharya, A., and Succop, P. A., 2000, Evaluation of Workers' Perceived Sense of Slip and Effect of Prior Knowledge of Slipperiness During Task Performance on slippery Surfaces. Am. Ind. Hyg Assoc. J., 61, Pp 492-500.

Council Directive 89/686/EEC, 21 December 1989. The approximation of laws of the member states relating to personal protective equipment (PPE). Official Journal of the European Communities No L 399, pp.18-38.

Gard, G. and Lundborg, G., 2000, Pedestrians on slippery surfaces during winter – methods to describe the problems and practical tests of anti-skid devices. Accident Analysis & Prevention, 32 (3), Pp 455-460.

Gard, G. and Lundborg, G. , 2001, Test of Swedish anti-skid devices on five different slippery surfaces, Accident Analysis & Prevention, 33 (1), Pp 1-8.

Grönkvist, R., 1995, A dynamic method for assessing pedestrian slip resistance. Thesis. Finnish Institute of Occupational Health, Helsinki.

Grönkvist, R., 1997, On transitional friction measurement and pedestrian slip resistance. In Proceedings of the International Ergonomic Association's 13th Triennial Congress (IEA'97). Vol 3. Pp 383-385. June 29- July 4, 1997, Tampere, Finland.

Grönkvist, R. and Mäkinen, H., 1997, Development of standards for anti-slip devices for pedestrians. In Proceedings of the Fifth Scandinavian Symposium on Protective Clothing. NOKOBETEF) (Ed. Nielsen, R. And Borg, C ) Pp 187-189, May 5-8, 1997, Danish Work Environment Fund, Elsinore, Denmark.

Hara, F., Kawabata, T., Sakai, N., Koboayashi, I., 1991, Safety of pedestrians walking areas in winter. In Proceedings from ISCORD 1991, Sapporo, Japan. Hirvonen, M., Leskinen, T., Grönkvist, R. And Saario, J., 1994, Detection of near accidents by measurements of horizontal acceleration of the trunk. International Journal of Industrial Ergonomics, 14, Pp 307-314.

Hirvonen, M., Leskinen, T., Grönkvist, R., Viikari-Juntura E. And Riihimäki, H., 1996, Occurrence of sudden movements at work. Safety Science, 24 (2), Pp 77-82. de Lange, A., Grönkvist, R., 1997, Bridging the gap between mechanical and biomechanical slip test methods. In Proceedings of the International Ergonomic Association's 13th Triennal Congress (IEA'97). Vol 3. Pp 368-370. June 29- July 4, 1997, Tampere, Finland.

Leclercq, S., 1999, The prevention off slipping accidents: a review and discussion of work related to the methodology of measuring slip resistance. Safety Science, 31, Pp 95-125.

Moe-Nielssen, R., 1999, Trunk accelerometer. A method for assessing balance under various task and environmental constraints. Thesis. Dept. Of Public Health and Primary Health Care, University of Bergen, Norway.

Sjögren, H. And Björnstig, U., 1991, Injuries to the elderly in the traffic environment, Accident Analysis & Prevention, 23, Pp 77-86.

ACKNOWLEDGEMENTS

This article is based on discussions, in preparing an application for development of a Nordic method to test anti- slip devices, with Mikko Hirvonen, Carita Aschan and Gunvor Gard to whom I am very grateful for their ideas and support in preparing the application.

Paper V ARTICLE IN PRESS

Applied Ergonomics 37 (2006) 177–186 www.elsevier.com/locate/apergo

Assessment of anti-slip devices from healthy individuals in different ages walking on slippery surfaces Ã Gunvor Garda, , Glenn Bergga˚rdb

aDepartment of Health Sciences, Lulea˚ University of Technology, Hedenbrova¨gen, SE-961 36 Boden, Sweden bDepartment of Civil and Environmental Engineering, Lulea˚ University of Technology, SE-971 87 Lulea˚, Sweden

Received 24 March 2004; accepted 30 April 2005

Abstract

The interest for effective preventive strategies for slips and falls is growing. Much remains to be done, however, to prevent slips and falls in the traffic environment. Using an appropriate anti-slip device may reduce the risk of slips and falls on different surfaces outdoors during winter. The aim of this study was to evaluate the best anti-slip devices of different designs in the Swedish market on a larger group of healthy individuals in different ages on five different slippery surfaces as a way to develop a standard method to test anti-slip devices. Three different designs of anti-slip devices: heel device, foot-blade device and whole-foot device were evaluated on ice surfaces uncovered or covered with gravel, sand, salt or snow. The evaluations were done according to subject’s perceived walking safety and balance, videorecordings of walking postures and movements, time to take on and off each anti-slip device, advantages/disadvantages with each anti-slip device and a list of priorities for own use according to three criteria: safety, balance and appearance. The heel device was perceived to be the most safe on all five surfaces, followed by the toe device and the whole-foot device. The heel device was also perceived to be the one with the best walking balance on uncovered ice and on snow covered ice. There were some significant differences due to gender and age. Most subjects walked with a normal muscle function in the hip and knee when walking with or without an anti-slip device on all surfaces. The heel device was perceived as the most rapid one to take on and the toe device as the most rapid one to take off. All three devices were perceived as having a good foothold. The heel device was perceived to fit the shoe and to be stable at heel-strike. The toe device was easily portable and stable on uncovered ice. The whole- foot device was comfortable to walk with and safe on snow covered ice. The heel device had the highest priority according to walking safety, walking balance and choice for own use. r 2005 Elsevier Ltd. All rights reserved.

Keywords: Anti-slip device; Slippery surface; Standard method; Evaluation; Balance; Walking

1. Introduction 1997; Gard, 2000a, b). The traffic environment can be a risky environment where pedestrians can be injured due Accidental falls are a common health problem and to slippery pavements and roads particularly in winter one-third of persons aged 65 or more fall at least once time. Research has showed that the main reasons for yearly (Tinetti et al., 1994). Injuries occur in approxi- injuries in the traffic environment for persons aged over mately half of the falls and 10% of them lead to serious 60 were falls, vehicle-associated events and other injury injuries (van Weel et al., 1995). To develop strategies to events (Sjo¨gren and Bjo¨rnstig, 1991). Two-thirds of the prevent accidents and injuries due to slips and falls is falls involved slipping on ice and snow. These injuries important (Gro¨nqvist, 1999; Redfern and Bloswick, accounted for 37% of the total cost of all injuries in the elderly in the traffic environment in Sweden. The Ã number of injuries increased as people grew older, and Corresponding author. E-mail addresses: [email protected] (G. Gard), women in their 50s showed the highest percentage [email protected] (G. Bergga˚rd). (Sjo¨gren and Bjo¨rnstig, 1991).

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The total risk for slip and fall accidents depends on decrease the forward velocity of the body (Gro¨nqvist et the interaction between individual behaviour, the task or al., 2001; Winter, 1991). activity to be performed and the external environment. Risk factors for slips and falls may be extrinsic Internal factors as individual factors and external (environmental factors) or intrinsic (human factors) or factors as environmental factors interact with each mixed (system factors) (Gro¨nqvist, 1995). The primary other. Methods to reduce the risks for slip and fall risk factor for slipping accidents is according to accidents need to deal with internal as well as external Gro¨nqvist, poor grip and low friction between the factors and the opportunity to handle risk situations, the footwear (foot) and the underfoot surface (pavement). coping ability (Gro¨nqvist et al., 2001). From the slipping point of view there are two critical Lord et al. (2001) have summarized and classified the gait phases in walking: heel-strike and toe-off (Strand- risk factors for accidents as psychosocial and demo- berg and Lanshammar, 1981). The heel-strike causes a graphic factors, postural stability factors, sensory and forward slip on the leading foot, whereas the toe-off neuromuscular factors, medical factors, medication causes a backward slip on the sole forepart, which can factors and environmental factors. There are also other be counteracted by stepping forwards with the leading factors that may be risk factors, such as age and gender. foot. The forward slip starting at heel-strike, would very Women participate more often in slip and fall accidents likely result in a dangerous fall backwards, due to the than men in ages below 80 years (Berg et al., 1997; fact that the forward momentum of the body maintains Bergland et al., 1998). The walking pattern can be seen the body weight on the slipping foot and allows the as a risk factor for slips and falls among both men and sliding movement to continue into a fall (Gro¨nqvist, women, such as a tripping walking pattern and short 1995). length of the footsteps. In analyses of walking patterns Comparative studies of friction measurement devices and walking problems, different aspects can be ob- show that a few devices are capable of simulating closely served: heel-strike, toe-off, length of steps, height of the force and motion in human gait (Gro¨nqvist, 1995). steps, symmetry of steps, rhythm of steps, rotation of A method for estimating the probability of slips and different parts of the body and deviations in walking falls based on measurements of available and required patterns (Gro¨nqvist et al., 2001; Gard, 2000a, b; Gard friction has been developed by Hansson et al. (1999). and Lundborg, 2000, 2001). Slips with recoveries and slips resulting in falls were Reduced postural control, i.e. disturbed balance, has recorded and categorized using a force plate and high- been put forward as a background factor to falls in the speed videocamera. The results showed that the number elderly (Tinetti et al., 1988). Reduced muscle strength in of slips and fall events increased as the difference the lower extremities and reduced mobility and function between the required and the measured coefficient of have also been found to be background factors to falls in friction increased. This type of measurements and the elderly. An exercise to increase muscle strength and analysis could assist in the design of safer environments balance improves these functions and therefore reduces (Hansson et al., 1999). A recently published study the risk of falling in the elderly living in the community assessing floor slipperiness also indicates that both (Beyer, 2002). Good balance capacity is a complex objective and subjective measures of slipperiness are motor skill and a prerequisite for many daily tasks such important in field studies and that an average friction as walking and transfering (Berg, 1989). The risk of coefficient and subjective perceptions may be in fair slipping and falling depends also to a great extent on a agreement and both might be good indicators of person’s subjective awareness of the potential slipperi- slipperiness (Chang et al., 2004). ness of the actual conditions. It may be easier to adapt In Europe, the work concerning EC type-examination one’s gait when a slippery condition is steady than when and certification of Personal Protective Equipment for unexpected changes in slipperiness occur. However, no anti-slip protection (also called anti-slip devices) is accident or injury statistics are available to confirm this mainly the responsibility of CEN Technical Committee hypothesis (Gro¨nqvist, 1999). TC 161 (foot and leg protectors). The essential health There are five critical motor functions during the gait and safety requirements for the design, construction and cycle in order to achieve safe propulsion of the body manufacturing of personal protective equipment includ- (Gro¨nqvist et al., 2001; Winter, 1991). These functions ing anti-slip devices are set forth in the directive 89/686/ are the maintenance of support of the body during EEC and its amendments, whereas the European stance, the maintenance of upright posture and balance standards have been worked out to devise practical of the total body, the control of foot trajectory to solutions as how to harmonize those essential require- achieve safe ground clearance and gentle heel or toe ments. Currently, there are no standards for anti-slip landing, the generation of mechanical energy to main- devices; therefore, these have been assessed directly tain the present forward velocity or to increase the against the essential health and safety requirements forward velocity and finally the absorption of mechan- stipulated in the Council Directive 89/686/EEC (Gro¨nq- ical energy for shock absorption and stability or to vist and Ma¨kinen, 1997). There is an urgent need to ARTICLE IN PRESS

G. Gard, G. Bergga˚rd / Applied Ergonomics 37 (2006) 177–186 179 develop European harmonized standards for anti-slip devices in use by workers at the workplace as well as for the elderly pedestrians and for other private users. The focus of the standard should be on assessing the preventive effect of the device, including ergonomic and functional aspects. There is a need for subjective and functional methods for testing and evaluating safety aspects of anti-slip devices. An appropriate anti-slip device can be used by the pedestrian, which may prevent the risk of slips and falls on ice and snow. When trying to improve the function of anti-slip devices and the possibilities of safe pedestrian movement during winter, methods to test anti-slip devices need to be developed. The aim of this study was to test the best anti-slip devices of different designs on the Swedish market on a larger group of healthy individuals in different ages on Fig. 1. Principal design of the anti-slip devices: heel device, foot-blade ﬁve different slippery surfaces as a way to develop a or toe device and whole-foot device. standard method to test anti-slip devices. 10 m

2. Material and methods Gravel on ice

2.1. Material Sand on ice

Snow on ice A total of 107 subjects from the general population in the Lulea˚and Boden area participated in the test of No coverage three anti-slip devices. There were 46 men and 61 women. They were aged 22–80, with a mean age of 51.1 Salt on ice years. In the study, one or two subjects from each age year 22, 23, 24 and so on up to 80 were selected. Fig. 2. Experimental set-up. Each track is 10 m long and 1 m wide. Inclusion criteria for participation in the experiment Some of the tracks are covered with different materials such as gravel, sand, snow and salt. were good balance, good mobility in hip, knee and foot and good muscle strength in the lower extremities. Basic 2.3. Experimental set-up functional abilities such as balance, mobility and basic muscle strength were evaluated by an experienced For the practical tests ﬁve different walking areas with physical therapist by observations of the subjects different slippery surfaces, each 10 m long, were functional performance in functional tests such as prepared (Fig. 2): functional reach (Duncan et al., 1992) and standing on one leg with eyes open and eyes closed, standing on heels and toes and walking on heels and toes. The subjects ice covered with sand (180 g/m2); performance was rated by the physiotherapist on rating ice covered with gravel (4–8 mm ca 150 g/m2); scales where the level of inclusion in the study was 3 or ice covered with 3–5 mm snow; more on a 4-level ordinal scale (Gard, 2000a, b). ice uncovered; ice covered with salt (9 g/m2). 2.2. Anti-slip devices tested To evaluate realistic walking situations in the trafﬁc The anti-slip devices were new in the Swedish market environment, such as a pedestrian crossing, the walking and represented three different designs of anti-slip cycle for each walking area was divided into six parts: devices: heel device, foot-blade device and whole-foot device (Fig. 1). The heel device, Icey, is manufactured by Brunnga˚rd AB (SE), the foot-blade device, Dubby, is 1. walk ‘‘normally’’ across the whole area; manufactured by Brunnga˚rd AB (SE) and the whole- 2. turn around; foot device, Bergsteiger, is manufactured by Rud 3. walk rapidly 4–5 steps; Kettenfabrik (DE). The sequence of the devices was 4. stop; randomized for each subject. The subjects had no earlier 5. walk backwards 4–5 steps; experience of using anti-slip devices. 6. walk ‘‘rapidly’’ across the whole area. ARTICLE IN PRESS

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Before the test each subject had the opportunity to How Do You perceive the walking safety of this anti-slip device? walk without anti-slip device on these six parts of the experimental walking cycle without stress, so they were Gravel Sand Snow Ice Salt No walking safety at all familiar with the situation. The experiment was designed Some walking safety to be a comparison between these ﬁve different slippery Fairly good walking safety conditions for each of the different designs of anti-slip Verygood walking safety devices. The subjects could use a helmet in the Fig. 3. Rating scale for ratings of perceived walking safety. experiment, if they wanted. No one used the helmet. No other safety precautions were taken. In the test situation each subject walked with each anti-slip device How Do You perceive the walking balance of this anti-slip device? on the ﬁve different slippery surfaces. The subjects were Gravel Sand Snow Ice Salt told to walk according to the instructions above. When No walking balance at all the experiments were performed the outdoor tempera- Some walking balance ture was appr. 5 1C and it was daylight. Fairly good walking balance Verygood walking balance

2.4. Methods Fig. 4. Rating scale for ratings of perceived walking balance.

After each practical test the subjects rated their Observation of walking posture and movements including normal muscle function in the walking safety (Fig. 3) and walking balance (Fig. 4)on hip and knee. each surface and described perceived advantages and 0 = Walking with adequate swaying up and down in knees 1 = Walking with straight knees, no swaying disadvantages with each anti-slip device. After the tests, 2 = Walking with straight knees, no swaying and raised shoulders the subjects own priorities regarding safety, balance and 3 = Walking with straight knees, no swaying, raised shoulders and a rigid posture appearance were noted. Observation of walking posture and movements in the rest of the body (head, shoulders Methods used in this study were rating scales for and arms) 0 = Walking with a relaxed head posture and relaxed movements in trunk, shoulders and arms perceived walking safety and balance, observations from 1 = Walking with head and trunk in a rigid posture and small movements in shoulders and arms 2 = Walking in a rigid posture without movements in head, trunk and shoulders, small movement videorecordings of walking postures and movements, in arms time to take on and off each anti-slip device, advan- 3 = Walking i a totally rigid posture tages/disadvantages with each anti-slip device and a list Observation of heel strike of priorities according to three criteria: safety, balance 0 = Very good dorsalflexion of the foot 1 = Fairly good dorsalflexion of the foot and appearance/own use. These methods have been 2 = Some, try to take a step by dorsalflexion of the foot developed earlier to describe functional problems in 3 = None, no dorsalflexion of the foot, take a step by flexion of the hip walking with different anti-slip devices and were found Observation of toe-off 0 = Very good plantarflexion of the foot to be reliable (Gard and Lundborg, 2000, 2001). The 1 = Fairly good plantarflexion of the foot percentage of agreement of the walking safety scale was 2 = Some, try to take a step by plantarflexion of the foot 3 = None, no plantarflexion of the foot or extension of the hip 86% and the corresponding agreement of the walking balance scale was 88% (Gard and Lundborg, 2000, Fig. 5. Observation of walking posture and movements in different 2001). Walking safety was defined to the subjects in Fig. parts of the body, heel-strike and toe-off. 3 as well as in the listing of priorities in Table 4 as their subjective perception of the safety of the surface they walked on in contrast to walking balance, which was use was also registrated. Each subject made a list of defined as the dynamics of the body posture to prevent priorities according to three criteria: safety, balance and falling (Winter, 1995). appearance (Gard and Lundborg, 2000, 2001). Four rating scales for evaluation of observed walking movements were also used (Fig. 5)(Gard and Lund- borg, 2000, 2001). The dimensions evaluated were: (1) walking posture and movements including normal 3. Results muscle function in the hip and knee; (2) walking posture and movements in the rest of the body (head, shoulders 3.1. Walking safety and balance and arms); (3) heel-strike; and (4) toe-off. All four dimensions were evaluated by observation scales ran- The subjects perceived that walking with an anti-slip ging from 0 to 3. Interreliability test of these scales has device could improve the walking safety on snow, ice shown the percentage of agreement between two and salt (Fig. 6). The heel device was perceived to be the observers to be 85%, 80%, 86% and 85%, respectively safest one on all five surfaces, followed by the toe device (Gard and Lundborg, 2000, 2001). A percentage of and the whole-foot device. The subjects perceived that agreement of 480% is considered as good (Altman, an anti-slip device can improve the walking balance on 1996). The subjective choice of anti-slip device for own snow and ice, but not on the other surfaces. The heel ARTICLE IN PRESS

G. Gard, G. Bergga˚rd / Applied Ergonomics 37 (2006) 177–186 181

110 100 90 80 Good 70 Fairly good 60 Bad 50 None 40 30 20 10 0 t l d w w w e e e e lt l lt lt e nd nd n nd o ow o ic ic c c a a a a v a a a n n o i i s s s s a s a s n n n n ravel r s s s s s sn o o n n n n g n n n n n n n o o o o on o n o o o o o o on o e e e e e e e o c ic ic ic c c e c e e e e e e e e vi v v v i i ic i e ic ic ic ic ic ic ic ic e e v v v v ic v v v v v v v v d d e e e e e e vice on g v e e e e e e e e l d d d d d d e d d d d d d d d o e t l d l l t N e o e t o e e Toe fo No e oe N oe oot No e o H H T foot No device on gravel o T f Toe fo le Toe de fo He H le Heel device on gravel le le o o le o o h h o h h W W h W W W

Fig. 6. Subjects (N ¼ 107) perceptions of walking safety after walking with each of the anti-slip devices: no anti-slip device, heel device, toe device and whole-foot device on gravel, sand, snow, ice and salt. Walking safety was evaluated as none, bad, fairly good or good.

110 100 90 80 Good 70 60 Fairly good 50 Bad 40 None 30 20 10 0 l d d e n ow alt avel an n ice s salt r sa sand s s n ice nice gravel n n o on on ngravel n e o on snow ce ice on ice on ice c e vi v vice on salt ic vice on e e evi vice o v e d device o dev de evice on g e l d device on salt device d device on device o el e e d d o t device on snow N e oe No d ot de N oo el device on snow H T To No oe o Toe device of No e Toe He Heel device Ton grav f Heel device on sand H le le foot device o o h hole Whole foot Whole foot W W Who

Fig. 7. Subjects (N ¼ 107) perceptions of walking balance after walking with each of the anti-slip devices: no anti-slip device, heel device, toe device and whole-foot device on gravel, sand, snow, ice and salt. Walking balance was evaluated as none, bad, fairly good or good. device was perceived to be the one with the best walking anti-slip device on all surfaces (Fig. 8). They walked balance on ice and snow (Fig. 7). with adequate swaying up and down in their knees. Only There were some significant differences due to gender one or two subjects walked with straight knees without and age. When comparing gender, the heel device was any swaying, there were no differences in this aspect perceived to be significantly safer to use on gravel and between anti-slip devices or surfaces (Fig. 8). ice and the toe device significantly safer to use on sand, Most subjects also walked with normal movements in gravel, ice and sand by women compared to men. It the rest of the body when walking with or without an took significantly longer time for women compared to anti-slip device on all surfaces (Fig. 9). They walked men to walk on gravel and sand (T-test for two with a relaxed head posture and relaxed movements in independent samples). When comparing age, the heel trunk, shoulders and arms. Only a few walked with their device was perceived to be significantly safer to use on head and trunk in a rigid posture with small movements gravel and ice and the toe device significantly safer to in shoulders and arms. There were no differences use on sand, gravel, ice and sand by people aged more between anti-slip devices or surfaces in movements in than 40 years compared to people less than 40 years old trunk, shoulders and arms (Fig. 9). (T-test for two independent samples). No other compar- From 52 to 85 subjects walked with a very good isons between devices and/or surfaces showed any dorsalflexion of the foot when walking with or without significant differences between gender or age. an anti-slip device (Fig. 10). From 10 to 23 subjects walked with fairly good dorsalflexion, from 12 to 24 3.2. Movement analyses with some dorsalflexion, trying to take a step by dorsalflexion of the foot. There were no differences Most subjects walked with a normal muscle function between anti-slip devices or surfaces in observed in the hip and knee when walking with or without an dorsalflexion of the foot (Fig. 10). ARTICLE IN PRESS

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110 100 90 80 3 70 60 2 50 1 40

0 30 20 10 0 l l e e el d w w w e lt vel v v v nd o ic ice alt alt a a ra ra ra and n e e ice s s s g sa snow sno sno s re r n n n g g n n n n u o n n n on s o o o o o o eo eo e e e eo ice on salt c ice c ic ice v vi v vi v v e on pure ice eonpu evic evic evice evic on gr e evice on sand e ce on p ic c d d d d device on san de de vi v vi l lde device d e l d e e e oe d ot de No e ot e No T o o No device To No d He f To f Heel He Toe devic foot e Hee e le foot device on le No d ol l o Heel de Toe device on footpur h ho ho le W W Wh W ho W

Fig. 8. Frequency of subjects with different observations (0–3) concerning walking posture and movements including normal muscle function in the hip and knee (N ¼ 107). 0 ¼ Walking with adequate swaying up and down in knees; 1 ¼ walking with straight knees, no swaying; 2 ¼ walking with straight knees, no swaying and raised shoulders; 3 ¼ walking with straight knees, no swaying, raised shoulders and a rigid posture.

110 100 90 80 3 70 2 60 1 50 40 0 30 20 10 0 l l l e e e w w w e e e t lt v v v o o o ic ic ice ic al a a ra ra n n n salt salt s s r sand sand sand sand snow s s s re re re re n n n g gravel g g u n n n n n n n n n n n u on o o o n o o o o o o o o pu pu p p e e e o o o n n n c c e e o n ic i i c ic ice o o o v v i v e e e e ev e v c c c d d device d devic e device device o ev e i i i d device device device t device device d device v v v e o o l e td e e e No eel o oot No N e o o d d device d T f eel Toe o No fo l t H Toe H He T e o Heel le No oe o o He T f h le Whole Whole f o Whole foot W h W

Fig. 9. Frequency of subjects with different observations concerning walking posture and movements including movements in the rest of the body (N ¼ 107). 0 ¼ Walking with a relaxed head posture and relaxed movements in trunk, shoulders and arms; 1 ¼ walking with head and trunk in a rigid posture and small movements in shoulders and arms; 2 ¼ walking in a rigid posture without movements in head, trunk and shoulders, small movement in arms; 3 ¼ walking in a totally rigid posture.

110 100 90 80 3 70 2 60 1 50 0 40 30 20 10 0 l l e e el d w e e lt lt lt vel v v v ow o ic ic a alt a a ra ra ra and an n e e ice s s s g s s snow snow sn s re r n n n g g n n n n n u n n n o o o o o o p e e e n ice on sa c ice ic ice o v vi v vice on sand vic v e on pure ice eonpu evic on gr e ev ic c device o device o de d de device on de de v vi l lde device o d l e t device on sand e e e oe device o No e device on pur No T oot No device To No l d t d He f To foot Hee Heel Toe d foot device e Hee e le foo le No device o oo ol l o Hee Toe f h ho ho le W W Wh W ho

Fig. 10. Frequency of subjects with different observations concerning heel-strike (N ¼ 107). 0 ¼ Very good dorsalflexion of the foot; 1 ¼ fairly good dorsalflexion of the foot; 2 ¼ some, try to take a step by dorsalflexion of the foot; 3 ¼ none, no dorsalflexion of the foot, take a step by flexion of the hip.

Nearly all subjects walked with a very good toe-off take a step by plantarflexion of the foot when with all anti-slip devices on all surfaces. Only 2–8 walking with the toe device. No subject had problems subjects had fairly good plantarflexion of the foot. A with toe-off when walking without any anti-slip device few, 3–4 subjects, had some plantarflexion, trying to (Fig. 11). ARTICLE IN PRESS

G. Gard, G. Bergga˚rd / Applied Ergonomics 37 (2006) 177–186 183

110 100 90 80 3 70 2 60 1 50 40 0 30 20 10 0 l l l e e d d d d e e e lt lt lt e v v n n n w w w w c c c a v a n a o o o o i i ice i a a ra r ra a a a n n n n e s salt s s gravel g g s s s s s s s s e r re re n n n n g n n n n n ur u u u o o o o n n n n o o o n n n p p p p o o o o o o o o e e e e e n n n n ic ic ic ic ic ic o o o o v v v v e ev ev e e e e e d device device d d ic c d l device device d d device o device device device device v vi e o l e e e o el e No foot No N e oe No oe d device device He T foot device T foot T foot l e e Heel Toe H e He e o l le l le No T foot d o o o o He h h h h W W W W Whole

Fig. 11. Frequency of subjects with different observations concerning toe-off (N ¼ 107). 0 ¼ Very good plantarflexion of the foot; 1 ¼ fairly good plantarflexion of the foot; 2 ¼ some, try to take a step by plantarflexion of the foot; 3 ¼ none, no plantarflexion of the foot or extension of the hip.

No signiﬁcant differences were shown between men/ Table 1 women and young/older people concerning the move- Time to take on and off the anti-slip devices: heel, toe and whole-foot ment analyses. Device Heel Toe Whole-foot

Time to take on 10 (5–30) 11(4–25) 15 (10–30) 3.3. Time to take on/off and advantages/disadvantages Time to take off 6 (4–8) 4 (2–8) 6 (4–8) Mean values (range) in seconds for the 107 subjects. The heel device was perceived as the most rapid one to take on and the toe device as the most rapid one to take Table 2 off. No significant differences were noted in time to take All possible advantages and disadvantages mentioned on or off between the devices (Table 1). Advantages mentioned were that all three devices were perceived as Heel Advantages Fit the shoe, stable at heel-strike, good foothold having a good foothold. The heel device was perceived Disadvantages Unstable at toe-off, changed movement pattern to fit the shoe and to be stable at heel-strike. The toe Toe device was easy portable and stable on ice. The whole- Advantages Easy portable, good foothold, stable on ice foot device was comfortable to walk with and safe on Disadvantages Do not fit all shoes, uncomfortable, can feel the snow (Table 2). spikes Whole-foot Some disadvantages were also mentioned. The heel Advantages Good effect in snow, good foothold, comfortable device was unstable at toe-off, the toe device was to walk with felt to be uncomfortable and did not fit all shoes and the Disadvantages Moving under the foot, clumsy and ugly, bad subject could feel the spikes. The whole-foot device balance from side to side was perceived to be clumsy and ugly and moved under the foot which reduced the perceived balance Table 3 (Table 2). Subject0s first priorities according to own use concerning walking safety, walking balance and choice for own use (N ¼ 107)

Device Heel Toe Whole-foot 3.4. Choice for own use Walking safety 47 34 26 Each subject’s choice of an anti-slip device for own Walking balance 42 31 34 use according to three criteria—walking safety, walking Choice for own use 52 35 20 balance and choice for own use—was registered. The heel device had the highest priority according to walking safety, walking balance and choice for own use (Table 3). Table 4 Each subject also gave their opinions about the Subject’s ﬁrst priorities about what characterize a good anti-slip device characteristics of a good anti-skid device in general Easy to take on and off 60 (Table 4). The most important aspects were that an anti- Stability, security while walking, good foothold 53 slip device must be easy to take on and off, be safe to Anti-slip device cover the whole foot 21 walk with and give a good foothold, be comfortable to Anti-slip device do not inﬂuence the walking pattern 14 Comfortable to wear and walk with 22 wear and cover the whole foot (Table 4). ARTICLE IN PRESS

184 G. Gard, G. Bergga˚rd / Applied Ergonomics 37 (2006) 177–186

4. Discussion best in walking safety and balance. The adaptation to slipperiness involves a maximization of stability through There are three different designs of anti-slip devices postural changes during early stance and midstance on the market that supports different phases in the (Llewellyn and Nevola, 1992). The body’s centre of mass normal gate: heel device for safe heel-strike, foot-blade is moved forward, facilitating a softer heel landing and device for safe toe-off and whole-foot device for both plantarflexion is greater than during a normal contact these phases. The selection of used devices are based on phase, thus reducing the heel contact angle with respect our earlier research identifying good examples of anti- to the floor. So the shoe/floor contact area appears to slip devices in each of the design groups (Gard and increase during heel touch-down. Due to lower shear Lundborg, 2000, 2001). forces available in the shoe/floor interface, the ground The results showed that walking with an anti-slip reaction profiles are altered for minimizing frictional device could improve walking safety on snow, ice and utilization aiming at reducing the vertical acceleration salt and perceived balance on snow and ice. The heel and forward velocity of the body (Llewellyn and device was perceived to be the best in both walking Nevola, 1992). Using a heel device may imply a more safety and perceived balance on all five surfaces. It was focused and gentle heel-strike and accordingly increase perceived to have good foothold and to be stable at heel- the heel device/surface area during heel touch-down. strike. On the other hand, it implied an unstable toe-off This may be another explanation to why the heel device and a change in movement pattern, with a clear heel- was selected as the best in walking security and balance. strike but a more insecure and unbalanced toe-off. A whole-foot device should be supporting a normal However, most subjects walked with a normal muscle gait. In our study, the whole-foot device did not fit function in the hip and knee as well as with normal properly to some of the subjects shoes, thus reducing movements in the rest of the body when walking with or this support. Therefore, the heel device was considered without each of the anti-slip devices on all surfaces. The to be the best device. The experimental set-up with five toe device was selected as the second and the whole-foot slippery surfaces is a realistic situation and the sequence device as the third concerning walking safety and of the devices was randomized for each subject. No balance. The toe device was perceived to be stable on specific safety precautions were taken during the ice, but it did not fit all types of shoes and the spikes experiment. This may have reduced the walking pace could be identified under the foot. The whole-foot device to a slower pace in the ‘‘walking rapidly phase’’ was perceived as good on snow but it was perceived by compared to if safe precautions had been arranged. As some subjects to be clumsy and ugly and moved under a precaution in this study the subjects had the the foot which reduced the perceived balance. The opportunity to walk without anti-slip devices on the gender differences concerning the foot-blade device surfaces before the experiments. The study took place might origin from the experiences from most females on a constructed ice area outside a laboratory. The area walking in high heel shoes, thus using the foot-blade was slightly inclined sideways (0.25%), which is more for safe walking. Research has shown that heel- approximately the same as a normal sidewalk in strike and toe-off are the most relevant parts of the Sweden. The ice surface was even. Not rough or covered walking cycle in relation to slipping risk (Strandberg with tracks from cars as it normally might be. This is and Lanshammar, 1981). The primary risk factor for representative for all kinds of slippery surfaces. Further slipping accidents according to Gro¨nqvist (1995) is poor studies ought to be done on other surfaces such as grip and low friction between the footwear (foot) and surfaces made from hard packed snow, rough surfaces, the underfoot surface (pavement). It is notable that in inclined surfaces in the walking direction (2%, 5%, 8% this study the heel device was perceived to have good and above 8%). No more than 2% is supposed to be a walking safety and balance. good standard for walk- and bike-roads close to From a safety point of view, there are two critical gait crossing and 5% and 8% are slope standards for phases in walking. First, the early heel contact and adopting the special requirements for disabled people second the moment of toe-off. The heel contact is in Sweden. To be able to draw a conclusion concerning considered to be more challenging for stability and more the importance of safety precautions such as the hazardous from the slipping point of view than the toe- influence of the using/not using of helmets or other off phase, because the forward momentum maintains equipments, further studies should be made. the body weight on the leading foot causing a forward What methods could be recommended in a European slide of the foot (Redfern et al., 2001). A gentle heel- standard for anti-slip devices? In our opinion, both landing also reduces collision-forces in the shoe/surface subjective and objective methods must be used. The interface during weight acceptance, a factor important methods used in our study were all practical, functional for maximizing friction and slip resistance in water, oil and user-friendly and can be used in a Nordic and later a and snow (Gro¨nqvist, 1999). This can be one explana- European standard. Videorecording of the walking cycle tion to our result as the heel device was considered the with a focus on heel-strike and toe-off is important with ARTICLE IN PRESS

G. Gard, G. Bergga˚rd / Applied Ergonomics 37 (2006) 177–186 185 analyses of similarities and differences in walking slip devices both subjective and objective methods movements and postures between anti-slip devices and should be recommended. surfaces. We used two videocameras for registration of body movements. In the future, more advanced videoe- quipment can be used, focusing directly on the feet References during the walking cycle, particularly focusing on heel- strike and toe-off, as they are the most relevant parts to Altman, D., 1996. Practical Statistics for Medical Research. Chapman study. Reliability test of a good and simple videoregis- & Hall, London. Berg, K., 1989. Balance and its measure in the elderly: a review. tration method focusing on heel-strike and toe-off can Physiother. Canada 41, 240–246. be recommended. The results showed that movements in Berg, W.P., Alessio, H.M., Mills, E.M., Tong, C., 1997. Circumstances the rest of the body were not so important when walking and consequences of falls in independent community-dwelling with anti-slip devices, compared to heel-strike and toe- older adults. Age ageing 26, 261–268. off. We recommend that further videorecordings also Bergland, A., Pettersson, A.M., Laake, K., 1998. Falls reported among elderly Norwegians living at home. Phys. Ther. Res. Int. 3, include a focus on abduction of the legs to identify if it is 164–174. relevant for safe walking and may differ between Beyer, N., 2002. Physical training reduces risk factors for disability and surfaces. Safe walking on slippery surfaces are not so falls in elderly women. Ph.D. Thesis, University of Copenhangen. easy to study, as it is influenced by each individual’s Chang, W.R., Li, K.E., Yueng-Hsiang Huang, Y.H., Filiaggi, A., momentary limits of stability, which may vary over time Courtney, T.K., 2004. Assesing floor slipperiness in fast-food restaurants in Taiwan using objective and subjective measures. and type of slippery surface. However, we recommend Appl. Ergon. 35 (4), 401–408. that the variables step length and walking cycle time can Duncan, P.W., Studenski, S., Chandler, J., Prescott, B., 1992. be included in further studies as they have been shown Functional reach: predictive validity in a sample of elderly male to be important for a safe walking and may reveal veterans. J. Gerontol. 47, 93–98. differences between different slippery surfaces (Gro¨nq- Gard, G., 2000a. Prevention of slip and fall accidents. Risk factors— methods—suggestions for prevention. Phys. Ther. Rev. 5, 177–184. vist et al., 1974). In a European standard for anti-slip Gard, G., 2000b. Prevention of slips and fall accidents: risk factors, devices, step length and walking cycle time ought to be methods and suggestions for prevention. Phys. Ther. Rev. 5, recorded and compared between anti-slip devices and 175–182. surfaces. Gard, G., Lundborg, G., 2000. Pedestrians on slippery surfaces during It is important, as shown in earlier research, to include winter—methods to describe the problems and practical tests of antiskid devices. J. Accid. Anal. Prev. 32, 455–460. both objective and subjective methods when assessing Gard, G., Lundborg, G., 2001. Test of anti-skid devices on five slipperiness (Chang et al., 2004). In a European different slippery surfaces. J. Accid. Anal. Prev. 33, 1–8. standard, the rating scales for perceived safety and Gro¨nqvist, R., 1995. A dynamic method for assessing pedestrian slip balance, the list of subjective priorities for own use and resistance. Thesis, Finnish Institute of Occupational Health, the listing of perceived advantages and disadvantages Helsinki. Gro¨nqvist, R., 1999. Slips and falls. In: Kumar, S. (Ed.), Biomechanics were functional and practical methods and could be in Ergonomics. Taylor and Francis, London (Chapter 19). recommended for further use. These methods can be Gro¨nqvist, R., Ma¨kinen, H., 1997. Development of standards for anti- included in a CEN-standard for type-examination of slip devices for pedestrians. In: Proceedings of Fifth Scandinavian anti-slip devices. Symposium on Protective Clothing, May 5–8, Elsinore, Denmark. Gro¨nqvist, R., Abeysekera, J., Gard, G., Hsiang, S., Leamon, T., Newman, D., Gielo-Perczak, K., Gubina, F., Hemami, H., McGee, R.B., 1974. On the dynamic stability of biped locomotion. IEEE 5. Conclusion Trans. Biomed. Eng. 21, 102–108. Gro¨nqvist, R., Chang, W.R., Courtney, T.K., Leamon, T.B., Redfern, In the observations no significant differences were M.S., Strandberg, L., 2001. Measurement of slipperiness: funda- found. Perceived differences were found. The subjects mental concepts and definitions. Ergonomics 44, b1102–b1117. Hansson, J., Redfern, M., Mazumdar, M., 1999. Predicting slips and gave heel device the highest priority according to falls considering required and available friction. Ergonomics 42. walking safety and balance, choice for own use and Llewellyn, M.G.A., Nevola, V.R., 1992. Strategies for walking on low- time to take on. Although it is not a whole-foot device, it friction surfaces. In: Lothens, W.A., Havenith, G. (Eds.), seemed to be very stable and comfortable to walk with Proceedings of the Fifth International Conference on Environ- and there were no parts that could come loose during mental Ergonomics, pp. 156–157. Lord, S.R., Sherrington, C., Menz, H.B., 2001. Falls in Older People. the walking. Cambridge University Press, Cambridge, UK. For all the 107 subjects, male and female from 22 to Redfern, M., Bloswick, D., 1997. Slips, trips and falls. In: Nordin, M., 80 years of age, both the objective and the subjective Andersson, G., Pope, M. (Eds.), Musculoskeletal Disorders in the methods were useful for comparing the properties of the Workplace. Masby Year Inc., pp. 152–166. anti-slip devices. Redfern, M.S., Cham, R., Hirvonen, M., Lanshammar, H., Marpet, M., Pai, Y.C., Powers, C., 2001. Biomechanics of slips. Ergonomics Further studies are needed to eventually be able to 44, 1138–1166. exclude some of the different tests used in this Sjo¨gren, H., Bjo¨rnstig, U., 1991. Injuries to the elderly in the traffic experiment. In an European standard for testing anti- environment. Accid. Anal. Prev. 23, 77–86. ARTICLE IN PRESS

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Paper VI For publication in the Journal of Safety Science

Criteria for use of anti-slip devices – towards a standardized test method.

Berggård, G.,*Gard, G.**, Hirvonen, M.*** and Aschan, C.*** *Dept of Civil, Mining and Environmental Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden. ** Dept of Health Sciences, Luleå University of Technology, SE-971 87 Luleå, Sweden. Sweden and Dept of Physical Therapy, Lund University, Box 5134, SE-220 05 Lund, Sweden. *** Finnish Institute of Occupational Health, Work Environment Development, FI-00250 Helsinki, Finland.

Abstract

Problem Slips and falls on ice and snow causes injuries. Falling due to slipping on icy surfaces may be prevented by using anti-slip devices. The aim of this study is to describe the criteria and methods for a European standard for anti-slip devices.

Method Tests were performed on three different types of anti-slip devices: a heel device, a foot blade device and a whole foot device. Objective and subjective methods were used.

Results The test results showed good agreement from the different methods used. The heel device performed best.

Discussion Criteria considered important for using anti-slip devices and methods, to be used in a European standard for testing anti-slip devices, were listed. Some further studies are needed.

Summary In a European standard for testing anti-slip devices, both subjective and objective methods should be considered. Further studies to identify objective methods comparable to the subjective methods used in our studies should be made. Age and gender aspects of safe walking on snow and ice should be considered.

Impact on Industry By establishing a standard, the industry can adopt their products to the stipulated requirements.

Key words: Anti-slip device, icy surface, test methods, standard, evaluation, pedestrian.

Problem Injuries from falls are common health problems in many European countries. More than one-third of persons 65 years or older fall each year (Tinetti, 2003). Injuries occur in approximately half of the falls, of which 10% lead to serious injuries, such as hip (and other) fractures, subdural haematoma, soft tissue injury, or head injury (van Weel et al, 1995). The traffic environment is a risky environment, and the main reasons for traffic environment injuries for persons aged over 60 are single-pedestrian falls, vehicle-associated events and other injury events (Sjögren & Björnstig, 1991). Two-thirds of these falls involve slipping on ice and snow. It is estimated that these injuries accounted for 37% of the total cost of all traffic environment injuries to the elderly in Sweden at that time. The number of injuries is increasing as people grow older (Sjögren & Björnstig, 1991). A later study shows that slipping on ice or snow during the winter in the health district of Umeå, northern Sweden caused 3.5 injuries per 1,000 inhabitants (Björnstig et al, 1997). The total cost of these injuries for one season, including emergency care and sick benefits, was estimated at 6.2 million SEK (1 million USD), at an average cost of 15,000 SEK (2,300 USD) per injured. The costs of outpatient and inpatient care were almost equivalent (90%) to the cost of all traffic injuries during the same time period. In a study (Öberg et al, 1996) of three medical districts in Sweden, i.e. Umeå, Lidköping and Göteborg, an average of approximately 2 injuries from falling per 1,000 inhabitants occurred during the winter. The average cost per incare patient was estimated at 43,000 SEK (7,100 USD) and 2,000 SEK (310 USD) per polyclinic treated patient.

Studies in Finland regarding the maintenance of pedestrian and bicycle routes (Perälä & Vuoriainen, 2002) show that during a 5-month winter period in 1999-2000, an average of 4.7 falls took place among pedestrians and bicyclists (the majority occurring among pedestrians) per day in Helsinki, 1.9 in Jyväskylä and 1.6 in Oulu.

Studies in the city of Sapporo, Japan showed that 111 people were hospitalised in December 1987 (Hara et al, 1991) and as many as 351 were hospitalised during December 2001 due to slips and falls (Shintani et al, 2003). The number of pedestrians taken by ambulance because of fall related injuries during the winter in Hokkaido, Japan has increased from 120 in 1984 to 503 in 1994 and 831 in 2004 (Takahashi et al, 2007).

In Sweden, approximately 15,000 females and 10,000 males are estimated to seek medical care each year after slipping on snow or ice, based on registrations in EHLASS (European Home and Leisure Accident Surveillance system) (Swedish Consumer Agency, 2003). This means 2.7 per 1,000 inhabitants.

The total risk for injuries from slips and falls depends on the interaction between individual behaviour, the activity performed and the external environment. Methods to reduce the risks for injury from slips and falls concerns both internal and external factors, as well as the opportunity to handle risk situations, i.e. the coping ability (Grönqvist et al, 2001). Lord et al (2001) have summarised and classified the risk factors for falls as being related to psychosocial and demographic, postural stability, sensory and neuromuscular, medical, medication and environmental. Individual factors such as age, gender and weight also exist. Women younger than 80 years of age suffer more from injuries involving slips and falls than men of the same age (Bergland et al, 1998). Walking ability and walking patterns can be seen as risk factors for slips

and falls among both men and women. Risky walking patterns and situations have been identified, including a tripping walking pattern, rough and uneven surfaces, and short footsteps. By analysing walking patterns, different aspects can be observed: heel strike, toe off, length of steps, height of steps, symmetry of steps, rhythm of steps, rotation of different parts of the body and deviations in walking patterns (Grönqvist et al, 2001; Gard, 2000; Gard and Lundborg, 2000 and 2001). There are two critical gait phases in walking from the slipping point of view: heel strike and toe off (Strandberg and Landshammar, 1981; Grönqvist et al, 1989). The heel strike causes a forward slip on the leading foot, and toe off causes a backward slip on the front part of the sole, which can be counteracted by stepping forward with the leading foot (Grönqvist, 1995). According to Grönqvist, the primary risk factor for slipping is poor grip, i.e. low friction between the footwear and the underfoot surface, considered especially true during winter when walking surfaces are covered with ice and snow. Developing strategies to prevent injuries due to slipping and falling is important (Grönqvist, 1999; Redfern and Bloswick, 1997; Gard, 2000).

Falling injuries due to slipping on icy surfaces may be prevented by using anti-slip protection, so- called anti-slip devices. Anti-slip devices are category II personal protective equipment (PPE), as clearly stated in the guide for the categorisation of personal protective equipment in the book entitled “Useful facts in relation to the personal protective equipment (PPE) directive 89/686/EEC”, published by the European Commission (1999 edition). It also states that “all equipment and/or accessories (whether or not detachable) designed and manufactured specifically to protect the foot and/or leg and to provide anti-slip protection” are PPE of category II, i.e. anti-slip devices must be type-examined before placed on the EU market. As an essential part of the EC type-examination process, appropriate tests deemed necessary to show conformity to the basic health and safety requirements of the PPE Directive should be carried out to check the conformity of PPE. Any European Notified Body to which notification has been given as stated in PPE Directive may conduct the EC type-examination for PPEs.

Essential health and safety requirements for the design, construction and manufacturing of personal protective equipment, including anti-slip devices, are set forth in the directive 89/686/EEC. The European standards have been worked out to devise practical solutions as how to harmonize these essential requirements. Work concerning standardisation of the EC type- examination procedure of Personal Protective Equipment (anti-slip protection) is mainly the responsibility of the CEN Technical Committee TC 161.

There are currently no standards for anti-slip devices, which have been assessed directly against the essential health and safety requirements stipulated in the Council Directive 89/686/EEC (Grönqvist and Mäkinen, 1997). Therefore, there is a need to develop a European harmonized standard for anti-slip devices used by workers outdoors as well as elderly pedestrians and other private users. The focus of the standard should be to assess the preventive effect of the device, including ergonomically and functional aspects. Also, when attempting to improve the functionality of anti-slip devices and the possibilities to safely walk during winter, methods to test anti-slip devices need to be developed. The aim of this study is to describe criteria and methods for a European standard for anti-slip devices.

Methods and materials

To develop test methods and criteria that be used as a basis for standardisation work of anti-slip devices, Luleå University of Technology in Sweden (LTU) applied most of the subjective test methods from this study in an outdoor test set-up, and the Finnish Institute of Occupational Health, Finland (FIOH) applied most of the objective test methods in a laboratory. The tests were performed on three different types of anti-slip devices: a heel device, a foot blade device and a whole foot device (Gard and Berggård, 2006). The heel device, Icey, and the foot-blade device, Dubby, are manufactured by Brunngård AB (SE); the whole foot device, Bergsteiger, is manufactured by Rud Kettenfabrik (DE). The devices are available on the Swedish and Finnish markets and were all previously tested according to the Council Directive 89/686/EEC. The devices were tested and compared with other devices and found to be the best detachable device of each type.

Experimental set up for tests of anti-slip devices in outdoor conditions For the practical tests, 5 walking areas with varying slippery surfaces, each 10 meters long, were used: ice with gravel (4-8 mm, ca. 150 g/m2), ice covered with sand (180 g/m2), ice covered with 3-5 mm snow, pure ice, and ice covered with salt (9 g/m2). The temperature was approx. -5°C. The snow was collected from previous snowfalls, stored at a cold location and evenly spread on the surface through a sieve. The study took place on a constructed ice area outdoors (Figure 1). The area was slightly inclined sideways (2.5%), approximately the same as a normal sidewalk in Sweden. The ice surface was even.

10 m

Gravel on ice

Sand on ice

Snow on ice

Pure ice

Salt on ice Figure 1. The experimental set-up in outdoor conditions. Each track is 10 m long and 1 m wide. Some of the ice tracks are covered with different materials, such as gravel, sand, snow and salt.

To evaluate realistic walking situations in the traffic environment, such as a pedestrian crossing, the walking cycle for each walking area was divided into six parts: 1) walk "normally" across the whole area, 2) turn around, 3) walk rapidly 4-5 steps, 4) stop, 5) walk backwards 4-5 steps and 6) walk "rapidly" across the whole area (Figure 1). The subjects used their ordinary winter shoes. The subjects could use a helmet if they wished, though nobody chose to. In the test situation, each subject walked with an anti-slip device on the five slippery surfaces (Gard and Lundborg, 2000 and 2001). The sequence of the devices was randomized for each subject. The subjects had no earlier experience of using anti-slip devices. In total, 107 subjects participated – 46 men and 61women, all aged 22–80, with a mean age of 51.1 years. In the study, 1 or 2 subjects from each age year, i.e. 22, 23, 24 and so on up to 80, were selected (Gard and Berggård, 2006).

The evaluations were done according to subject’s perceived walking safety and balance, video recordings of walking postures and movements, walking time, time to take on and off each anti- slip device, advantages/disadvantages with each anti-slip device and a priority list of person’s usage according to three criteria; safety, balance and appearance.

The following listed subjective methods were used in the experimental set up outdoors: • Ratings of walking safety and walking balance on each surface (Gard and Lundborg, 2000 and 2001). • List of advantages and disadvantages with each anti-slip device (Gard and Lundborg, 2000 and 2001). • Priorities for own use regarding safety, balance and appearance (Gard and Lundborg, 2000 and 2001).

The following listed objective methods were used in the experimental set up at outdoors: • Observations from video recordings of walking postures and movements (Gard and Lundborg, 2000 and 2001). • Time to take on and off each anti-slip device (Gard and Lundborg, 2000 and 2001). • Evaluation of observed walking movements (Gard and Lundborg, 2000 and 2001). • Also, the walking time was recorded (Gard and Berggård, 2006).

These methods were developed to describe functional problems in walking with different anti- slip devices and found reliable (Gard and Lundborg, 2000 and 2001). Four rating scales to evaluate the observed walking movements were also used (Gard and Lundborg, 2000 and 2001).

Observation of walking posture and movements, including normal muscle function in the hip and knee. 0 Walking with adequate swaying up and down in knees 1 Walking with straight knees, no swaying 2. Walking with straight knees, no swaying and raised shoulders 3 Walking with straight knees, no swaying, raised shoulders and a rigid posture Observation of walking posture and movements in the rest of the body (head, shoulders and arms) 0 Walking with a relaxed head posture and relaxed movements in trunk, shoulders and arms 1 Walking with head and trunk in a rigid posture and small movements in shoulders and arms 2 Walking in a rigid posture without movements in head, trunk and shoulders, small movement in arms 3 Walking in a totally rigid posture Observation of heel strike 0 Very good dorsalflexion of the foot 1 Fairly good dorsalflexion of the foot 2 Some, try to take a step by dorsalflexion of the foot 3 None, no dorsalflexion of the foot, take a step by flexion of the hip Observation of toe-off 0 Very good plantarflexion of the foot 1 Fairly good plantarflexion of the foot 2 Some, try to take a step by plantarflexion of the foot 3 None, no plantarflexion of the foot or extension of the hip Figure 2. Observation of walking posture and movements in different parts of the body, heel-strike and toe-off in outdoor conditions.

The dimensions evaluated were a) walking posture and movements including normal muscle function in the hip and knee, b) walking posture and movements in the rest of the body (head, shoulders and arms), c) heel-strike, and d) toe-off. All four dimensions were evaluated by observation scales ranging from 0 to 3 ( Figure 2). An inter-rater reliability test of these scales has shown the percentage of agreement between two observers to be 85%, 80%, 86% and 85% (Gard and Lundborg, 2000 and 2001). It is important to have as high an inter-rater reliability as possible. According to Nunnaly (1978), a good inter-rater reliability is over 0.7 (70%).

Objective laboratory test set up A slip-simulator device (Figure 3) was used to study the anti-slip devices in a laboratory. The method used is detailed in Grönqvist (1995). The measurements concentrated on evaluating the available dynamic coefficient of friction (DCOF) of the three studied anti-slip devices. The simulator models force levels and speed of human locomotion. The walking speed during normal gait is about 1.2 – 1.4 m/s. Human subjects generate force peaks about 1.2 times the body mass (at heel strike and toe off). A person weighing over 42 kg can generate peak forces of 500 N or more. A vertical force of 500 N and horizontal sliding speed of 0.4 m/s were used in the tests on the smooth ice surface. The ice surface temperature was adjusted to -5±1°C. Two different test modes were used: heel strike (five degrees contact angle with the footwear sole and ice) or foot flat (0 degrees contact angle). The heel mode was used with the heel type of anti-slip device and the flat mode with both the whole foot and foot blade models. Ten consecutive trials were performed with each device and the standard deviations (SD) of measurements were calculated.

Figure 3. Experimental setup in the laboratory.

The tensile strength of the devices in cold conditions were tested by preconditioning them in a thermal chamber (Arctest 500) for four hours at -20°C before testing them in the ambient room temperature of +20°C. A Lloyd LR10K tensile test machine measured the tensile strength. During testing, the machine had a uniform speed of 100 mm/s and the machine was run until the device broke or extension limits of the tensile testing machine were reached. The highest force and extension were taken as results. The devices were assumed to stand up to at least this kind of force because it is easily generated by hand when putting the devices on the shoes.

The corrosion resistance of the devices was tested in accordance with the standard EN ISO 20344 test methods for safety, protective and occupational footwear for professional use. The anti-slip devices were allowed to stand for 48 h in 1% aqueous solution of sodium chloride.

Practical performance of the devices was subjectively tested by three test persons who put the devices on footwear and took them off. The test persons also walked on the surface of smooth plywood plate and on rough concrete flooring.

Results

Results from the tests in the outdoor conditions No significant differences were found in the observations. The movement analysis made by an experienced physical therapist was based on the video recording showing only a few observations among the subjects concerning changes in walking posture and movements, including normal muscle functions in the hip and knee, walking with or without an anti-slip device on all surfaces. The situation was almost identical for observations concerning changes in walking posture and movements, including movements in the rest of the body and for changes in toe-off. Observations showed changes in heel strike on the different surfaces among 10 to 23 subjects (depending on the surface) (N=107) who walked with fairly good dorsalflexion, and from 12 to 24 subjects (also depending on the surface) (N=107) with some dorsalflexion, and attempting to take a step by dorsalflexion of the foot.

Other perceived differences were found. The subjects gave the heel device the highest rating according to walking safety and balance, choice for personal use and time to take on. Although it is not a whole foot device, it seemed very stable and comfortable to walk with and no parts came loose during walking. The heel device was perceived the safest on all five surfaces, followed by the foot blade device and the whole foot device. The heel device was also perceived to have the best walking balance on uncovered ice and on snow covered ice.

Most subjects walked with a normal muscle function in the hip and knee when walking with or without an anti-slip device on all surfaces.

The heel device was perceived as the quickest to take on and the toe device as the quickest to take off. All three devices were perceived as having good foothold. The heel device was perceived to fit the shoe and be stable at heel-strike. The toe device was easy portable and stable on uncovered ice. The whole-foot device was comfortable to walk with and safe on snow covered ice.

For all 107 subjects, both males and females aged 22 to 80, the subjective methods were useful for comparing the properties of the anti-slip devices.

There were some significant differences due to gender. The heel device was perceived to be significantly safer to use on gravel and ice and the toe device significantly safer to use on sand, gravel, ice and snow for females compared to males. It took significantly longer for females compared to males to walk on gravel and sand (T-test for two independent samples).

There were also some significant differences due to age. The heel device was perceived to be significantly safer to use on sand, gravel, ice and snow by people aged 40 and older compared to those aged 40 and younger (T-test for two independent samples).

Results from the laboratory test The dynamic coefficient of friction (DCOF) values and standard deviation (SD) for the devices on smooth ice are presented in Table 1.

Table 1. The dynamic coefficient of friction (DCOF) and standard deviation (SD) values on smooth ice for tested anti-slip devices. Type of device Brand DCOF SD Heel Icey 0.36 0.02 Foot blade Dubby 0.30 0.06 Whole foot Bergsteiger 0.26 0.02

The heel device showed the highest DCOF, and is thus the most efficient anti-slip device. The foot blade is the second best and the whole foot device the third.

Table 2 Tensile strength in the cold, of the devices maximum force (N) or maximum force (N) and extension (mm) if no break was detected. Device Tensile strength and extension Corrosion Item #1 Max Item #2 Max comments extension extension Icey 402 N 411 N Both samples broke no Dubby 248 N 424 mm 237 N 437 mm No break detected no Bergsteiger 203 N 317 mm 214 N 320 mm No break detected no

In the practical performance, all three devices received the same evaluation results. Three test persons evaluated that the devices were easy put on and take off the shoes. Walking was convenient when the devices were attached to the footwear.

Discussion The results from the laboratory test seem to correspond with the outdoor test findings. The same order among the devices was found. According to these tests, the heel device “the best”, as it is ranked as number 1 in both test set ups. The foot blade device the “second best” and the whole foot device the third.

The criteria for safe walking during both winter and summer should be based on a safe gait. Therefore, the ability to perform a correct walking cycle with a safe heel strike and toe off, the length, height symmetry and rhythm of steps as in normal walking, and the rotation of the upper body are all regarded essential criteria (Grönqvist et al, 2001; Gard, 2000; Gard and Lundborg, 2000 and 2001).

The subjects did not choose to wear any helmets during their walk. Therefore, their perception of risk might have been low or they might have adapted to a more cautious gait when anticipating slippery surfaces, as found by Cham and Redfern (2002). The foot blade model had the largest deviation of DCOF values (See Table 2). This might explain some of the differences in perceived walking safety compared to the heel device.

Female rated their walking safety higher when walking with both the heel or the toe device on gravel and pure ice. Females walked in a slower pace on gravel and sand, perhaps due to the fact that they walked more carefully in this experimental situation and that they did not rely on on the anti-slip properties of the used materials, gravel and sand. To attain dynamic stability of locomotion, the step length and walking cycle time control seem important (Gubina et al, 1974). In a European standard for anti-slip devices, step length and walking cycle time should be

recorded and compared between anti-slip devices and surfaces. Further studies on the gender differences are needed.

There were also some significant differences due to age. The heel device was perceived to be significantly safer to use on sand, gravel, ice and snow by people aged 40 and older. A laboratory study on sensory changes in the subjective assessment of the elderly on floor slipperiness showed an increased likelihood of slips and falls compared to younger subjects (Lockhart et al, 2002). In outdoor conditions in Sweden, elderly people are obviously expected to become injured more on slippery surfaces outdoors compared to younger people. The heel strike is of importance for not slipping and falling. Therefore, elderly subjects might have preferred an anti-slip device with secure heel contact, the heel device.

The severity of a slip and fall injury on snow and ice increases with age (Hosotani et al, 2007). This increase is higher for older females (NCO, 2005). Therefore the age and gender aspects of safe walking on snow and ice should be considered.

There are objective, combined and subjective human centred approaches to measure slipperiness (Grönqvist et al, 2001). The measurement of ground reaction forces is an example of the former rating scales for balance and safety, and utilized friction is an example of the latter rating scales.

Examples of vital criteria for safe walking during the winter are listed below: 1. Good walking safety and walking balance on each surface in experimental tests (Gard and Lundborg, 2000 and 2001). According to Holbein and Chaffin (1997), walking safety is defined as a stable posture where the body’s centre of mass is within the base of support. Walking balance is defined, according to Winter (1995), as a term to describe the dynamics of the body posture to prevent falling. This can be assessed by measuring subjective ratings regarding safety and balance (Gard and Lundborg, 2000 and 2001). 2. Easy to take on and off each anti-slip device, easy to carry. (Gard and Lundborg, 2000 and 2001). 3. No disadvantage that can cause unsafe walking or slipping and falling (Gard and Lundborg, 2000 and 2001). This means advantages that can improve: -security -safe walking -walking speed -reduction of the risk for an injury (from slipping and falling) -reduction of severity of an injury 5. Secure and safe design and construction of the anti-slip device, i.e. no loose features that can cause slips or falls or increased severity of injuries from slips and falls. 6. Other aspects, such as fear of falling, dependency on body and balance awareness, and perceived friction, could also be of interest in assessing anti-slip devices.

Most of them were tested by the authors of this article. The criteria and where they were used by the authors are listed in Table 3.

Table 3: Criteria for safe and secure walking during the winter. Criteria Comments Test location 1. Good perceived walking ability Combined preferences from the individual a) Good walking safety Surface relation towards the human being Outdoor b) good walking balance on each surface in Human dynamic balancing Outdoor experimental tests 2. No difficulties in handling: Easy to use a) taking on each anti-slip device, Outdoor b) taking off each anti-slip device, Outdoor c) easy to carry along when not in use Outdoor 3. Ability to perform a correct walking cycle: a) with a safe heel strike Outdoor b) with comfortable roll over Outdoor c) with safe toe off, Outdoor d) with length, - e) with height symmetry - f) with rhythm of steps as in normal walking, - g) with rotation of the upper part of the body Outdoor h) with good walking speed Outdoor 4. Possibilities to adapt to coping strategies in Alternative strategies used in walking is - walking through out all ages reduced during aging 5. Product properties a) no loose details that can cause slips or falls Laboratory b) materials -corrosion resistance of the metal parts tested Laboratory according EN ISO 20344 -tensile strength in cold conditions (-20 °C) minimum requirement of FIOH is 200 N -weight of the device c) design appearance (Outdoor) d) dynamic friction Laboratory f) soiling Dirty devices without special cases is (Outdoor) unattractive to carry along

The movement analysis conducted by an experienced physical therapist and based on video recordings did not show as large differences as the subjects made in their own evaluations. Therefore, the movement analysis in its present form could probably be excluded as one of the used methods. Video recording of the walking cycle should also probably not be included as a part of the testing for the EC-type approval process due to its high costs. The experiences obtained from research projects using this method should be taken advantage of so that, e.g., new testing methods yielding the same results could be developed to conduct analyses of the similarities and differences in the use of anti-slip devices on different surfaces.

Feet during the walking cycle should be the focus, particularly on heel-strike and toe-off, as they are the most relevant parts to study. Future research on the use of heel-mounted accelerometers and comparisons with a video registration method focusing on heel-strike and toe off are recommended. The use of heel-mounted accelerometers could provide a tool for the quantitative

measuring of slip distance in support of more qualitative measures, such as subjective ratings or observations (McGorry et al, 2007).

In a European standard to test anti-slip devices, both subjective and objective methods should be considered, as well as the nature of an EC-type approval process, where normally only one type is tested at a time. The price of testing should not be too high, since it is not possible for the manufacturer to apply a CE-type examination if the costs are too high compared to the price of an anti-slip device. The type of examination should be carried out in a reasonable time schedule, i.e. 2-3 months. FIOH also normally conduct practical performance tests with 3-persons in the type testing. It is common practice nowadays for footwear testing (EN 20344) to have restrictions, i.e. 3-persons ergonomic evaluation of the product. In the practical performance test the subjects should always wear a helmet. Therefore, a standard based mainly on objective measurements in controlled conditions should be preferred.

Summary The main issues of this study are what criteria are important for using anti-slip devices and what methods could be recommended for usage in a European standard for testing anti-slip devices. Most methods used in our study were practical, functional and user-friendly, and could be used in a European standard. Further studies to identify objective methods comparable to the subjective methods used in our studies should be made. Age and gender aspects of safe walking on snow and ice should be considered. A standard based mainly on objective measurements could thereafter be established.

Impact on Industry By establishing a standard the industry can more easily adopt their products to the stipulated requirements.

Acknowledgement This study has been financed by The Nordic Council, The Swedish Consumer Agency, The Swedish Rescue Services Agency and Luleå University of Technology. There is no conflict of interest. There is no financial relation or other to the manufacturers of the tested devices. The tested devices were bought from importers or retailers.

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Paper VII Accident Analysis and Prevention 42 (2010) 1199–1204

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Accident Analysis and Prevention

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Pedestrians in wintertime—Effects of using anti-slip devices

Glenn Berggård ∗, Charlotta Johansson

Department of Civil, Mining and Environmental Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden article info abstract

Article history: Pedestrians slipping and falling is a major safety problem around the world, not least in countries with Received 11 August 2009 long winters such as Sweden. About 25 000–30 000 people need medical care every year for treatment of Received in revised form 12 January 2010 fall injuries in Sweden. Use of appropriate shoes and anti-slip devices are examples of individual measures Accepted 19 January 2010 that have been suggested to prevent slipping and falling. An intervention study was performed during the period February to April 2008. The study, which Keywords: focused on healthy adults in northern Sweden, examined the effect of using anti-slip devices on daily Single-pedestrian walking journeys and prevention of slip and falls. Slip Fall The respondents were divided into three groups: an Intervention Group, a Control Group, with similar Anti-slip distribution of gender and age, and a Comparison Group. Four questionnaires were distributed: (1) back- Exposure ground, (2) daily diary of distance walked and occurrence of incidents or accidents reported weekly, (3) Wintertime detailed incident or fall report and (4) experiences of using anti-slip devices for those who used these devices during the trial period. Half of the respondents stated that they had previous experience of using anti-slip devices. In this study, 52% of the respondents used anti-slip devices. Anti-slip devices improve the walking capability during wintertime. Among those using appropriate anti-slip devices, the average daily walking distance was found to be statistically signiﬁcantly longer compared to people not using anti-slip devices. This study indicates that an increase in daily walking distance can be made without increasing the risk of slips/falls when using anti-slip devices. The study also indicates that by using appropriate anti-slip devices and having information about when and where to use them, based on their design, people avoid having slips and falls. The respondents experienced in using anti-slip devices in this study will continue to use them and will also recommend others to use anti-slip devises. © 2010 Elsevier Ltd. All rights reserved.

1. Introduction 2003). One explanation for this seems to be that women walk more than men, especially during the wintertime (Nordin, 2003). 1.1. Problem analysis In a pilot study in Luleå, Sweden, 4900 pedestrians were observed at a speciﬁc location where the surface conditions were slippery. Pedestrians slipping and falling is a major safety problem around Five incidents occurred, each of which had an estimated injury the world, not least in countries with long winters such as Sweden risk of 10 × 10−4. Pedestrians injured in single-pedestrian acci- and Finland. There are many injuries from slip and falls on snowy dents on slippery, icy or snowy road surfaces are, on average, more and icy surfaces in Sweden. About 25 000–30 000 people (3.2 per seriously injured than those injured on other surfaces (Berntman, 1000 inhabitants) need medical care every year for treatment of fall 2003). injuries. On average, every year there are more than two injuries per 1000 male inhabitants and more than three injuries per 1000 1.2. Countermeasures female inhabitants from falls on icy surfaces which are so serious that they need medical care. Females are over-represented; par- Measures to reduce the accident rate and/or the severity of ticularly in the age group 45–74. For this age group, women suffer accidents can be either community-based or based on individual from injuries from slips and falls on snow and ice almost twice as initiatives. Snow removal and anti-slip treatment are examples often as men (about 17 injuries from falls on snow and ice per year of community-based measures. Using appropriate shoes and anti- and 1000 inhabitants for women, and about 9 falls for men) (Nordin, slip devices are examples of individual measures that have been suggested (Björnstig et al., 1997; Lindmark and Lundborg, 1987; McKiernan, 2005; Nilsson, 1986). Normal snow clearance does not ∗ Corresponding author. Tel.: +46 920 491711; fax: +46 920 492818. appear to reduce the number of pedestrian falls (Elvik and Vaa, E-mail address: [email protected] (G. Berggård). 2004). A reduction of walking on icy or snowy roads by 10% is

0001-4575/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.aap.2010.01.011 1200 G. Berggård, C. Johansson / Accident Analysis and Prevention 42 (2010) 1199–1204 estimated to reduce the number of falling injury accidents by 15% (Control/Intervention) 43.3/41.8; women (C/I) 45.6/44.9). Median: (Elvik, 2000). Still, there is no study showing the benefits of using men (C/I) 40.5/38; women (C/I) 44/43.5. The Intervention Group anti-slip measures, such as snow removal and anti-slip treatment, and the Control Group were invited to separate information meet- or the use of personal safety equipment like individual anti-slip ings to discuss problems and benefits from walking during the devices (Öberg et al., 1996; Elvik, 2000). wintertime and the importance of the study. But not all respon- There are only a few studies, published anywhere in the world dents ended up participating in the information meetings, with 19 which have focused on the usage of anti-slip devices. A study among and 20 respondents respectively participating from each group. The women living in Sapporo, Japan, showed a relatively high number Intervention Group also received information about detailed usage of falls requiring medical attention (Hara et al., 1997). That study of different types of anti-slip devices. The members of the Inter- showed that 38% of all women used non-slip shoes and/or anti- vention Group were equipped with one of three different types slip devices with studs, knobs or ceramics on the soles, with 16.3% of anti-slip devices: a heel device, a foot-blade device or a whole (N = 1382) having detachable anti-slip soles. The anti-slip perfor- foot device. The Comparison Group was recruited from three other mance of their shoes and their experiences with anti-slip devices departments at LTU and was simply informed, in writing, about the were recorded. According to Hara et al. (1997) the people were not importance of their participating in a travel survey. Some respon- satisfied with the performances of the anti-slip devices. Methods to dents in the Control and the Comparison Groups used their own test anti-slip devices and assessments of anti-slip devices has been anti-slip devices. That is noted in the evaluations. Because we could made identifying effective devices (Gard and Lundborg, 2000, 2001; not ethically forbid already owners of anti-slip devices to use them Gard, 2000; Gard and Berggård, 2006). An intervention study was we analysed the differences between all the actual users compared conducted in the USA during the winter 2003/2004 among 109 fall- to all non-users (Fig. 1). prone respondents aged 65 and above. They completed 10 724 diary Four questionnaires were distributed: days. Participants were randomised to wear an anti-slip device or their ordinary winter footwear when walking outdoors. Seven I. Background, health, attitudes and usage of safety equipment in falls occurred with people using anti-slip devices. That study con- the beginning of the trial period. This form was answered by 67 cluded that wearing specific anti-slip devices reduces the risk of respondents. outdoor winter falls, and of minor falls especially among older peo- II. Daily diary of walked distance, walking conditions, occurrence ple with a history of previous falls (McKiernan, 2005). A pilot study of incidences or falls reported weekly. 61 respondents used this on the use of anti-slip devices was conducted in Finland in 2005 form for at least 1 week. (Juntunen et al., 2005). The 93 respondents (aged 21–80) suffered III. Detailed incident or fall description used after each occurrence three falls. Anti-slip devices or studded shoes were used in one of incidents or falls. This form was used at least once by 28 of those cases. The users of anti-slip devices and studded shoes respondents from all of the groups. reported improved walking capacity at nearly normal speed inde- IV. Experiences from using anti-slip devices during the trial period. pendent of weather. They also continued to conduct their daily There were 32 respondents from all of the groups who used outdoor routines and therefore maintained their fitness. The fear anti-slip devices; 18 of these respondents returned Form IV. of falling was also reduced among people wearing anti-slip devices (Juntunen and Grönqvist, 2006). The definitions of an incident and a fall were discussed and defined together with the respondents in the Intervention Group 2. Method and the Control Group in the information meetings before the trial period. An incident was defined as an occurrence of skidding, slip- An intervention study was performed from February to April ping, stumbling or by other means losing the balance when the 2008 at Luleå University of Technology (LTU) in Sweden. The study, respondent needs to correct or take some action in order not to fall. which focused on healthy adults in northern Sweden, examined A fall was defined as an occurrence when a part of the body other the effect of using anti-slip devices on daily walking distances and than the feet was in contact with the ground. prevention of slip and fall accidents. This study differs from earlier The address of the location where the incident or fall took place, studies by recording the exposure, in km and in time, and the usage and the local weather data from the closest located Swedish Meteo- of different walking aids such as anti-slip devices, or walking poles, rological and Hydrological Institute (SMHI) meteorological station and its influence on slipping and falling. The detailed objectives of were used in the analysis. The weather conditions in Northern this study were to answer the following research questions: Sweden during February to April are typically cold and snowy. The temperature ranges from around -30 ◦C in the beginning of • What are the respondent’s previous experiences of using anti-slip the period to +10 ◦C during the daytime at the end of the period. devices? The ground is typically covered with snow. The snow has been • Are there any differences in exposure between respondents using compressed and also transformed to ice especially on pedestrian anti-slip devices compared with non-users? surfaces. There are frequent snowfalls throughout the winter. • Are there any differences in incidents or falls? The questionnaires and local weather data were analysed using • Are there any differences in the exposure/risk relationship? a statistical package called SPSS 15.0.0. • What are the experiences of using anti-slip devices?

The respondents were recruited among employees from depart- 3. Results ments at LTU. The respondents for the Intervention Group and the Control Group were recruited from two departments to par- 3.1. Description of data ticipate in a health promoting project. These individuals was gender-separated (N (men) = 34, N (women) = 31). 17 men and The respondents in the different groups showed similar distri- 15 women were randomly selected for the Intervention Group, bution with respect to gender and age, in the Intervention Group while the remaining sample was assigned to the Control Group. the age of the respondents were 30–67 years, in the Control Group Based on age distribution – the only relevant variable available it were 27–64 years and in the Comparison Group it were 30–66 – randomisation was deemed reasonably successful (Mean: men years. The share of females was in all groups 60%. G. Berggård, C. Johansson / Accident Analysis and Prevention 42 (2010) 1199–1204 1201

3.2. Earlier experiences of walking during wintertime and use of 3.3. Analysis of the daily diary (Questionnaire II) anti-slip devices (Questionnaire I) Overall, 2738 daily diary forms were returned. Partial dropout The respondents recorded their previous experiences of falls occurred. Actual numbers of respondents participating are pre- during the winter season 2007/2008, their behaviour in different sented in Table 1. outdoor conditions and their attitudes towards the use of different There is no significant difference between the groups with safety equipment. respect to mean daily total walking distance and mean daily total Sixteen respondents had experienced one fall and eight respon- walking time. For the respondents, independent of group, using dents two falls. Two of the previously experienced falls occurred anti-slip devices, the mean daily total walking distance is longer, while using anti-slip devices. Particularly in the Intervention Group, 4.08 km, during days using anti-slip devices, compared with peo- the experiences of previous falls were similar for women and men. ple not using anti-slip devices, 2.66 km (see Table 2), a significant In the Comparison Group, nearly all the previous falls were among difference (df = 1, F = 86.139, p < 0.05). men. Women were 11 of in total 24 respondents indicating that This is particularly true for those in the Control Group, where there is no significant difference between genders with respect to the walking distance is 6.51 km for anti-slip users compared with experience of falls during the part of the winter season 2007/2008 2.65 km for non-users. There is a statistical significant difference which occurred prior to these experiments. between the Intervention Group and the Control Group among Roughly one third (35%) of the 67 respondents stated that they anti-slip users with respect to mean total daily walking distance reduce their walking distances when surfaces are slippery and 23% (mean difference = −2833.339, p < 0.05) independent of usage at reduce their walking during snow falls. Also, 23% stated that they that time, and mean distance with anti-slip devices (mean differ- never used anti-slip devices and 27% stated they seldom used anti- ence = −2523.890, p < 0.05). There are no such statistical significant slip devices prior to this. Nearly one third of the 40 females had differences between the Intervention Group and the Comparison experience in using anti-slip devices. And they stated that they Group. often but not always, or always, use the devices. The importance Respondents aged 45 years and above walked significantly of using anti-slip devices is seen as strong especially among the longer distances, in mean daily total walking distance 3.21 km respondents in the Intervention Group; 44% stated that anti-slip compared to 2.48 km and when using anti-slip devices 4.19 km devices are very important. In the Control Group, that percentage compared to 1.73 km respectively. There are statistical differ- was 25% and in the Comparison Group it was 29%. Five respon- ences between older and younger respondents for both the mean dents stated that they always use anti-slip devices. (However, these daily total walking distance for all respondents (df = 1, F = 43.277, answers were reported after the respondents in the Intervention p < 0.05) and the distance with anti-slip devices (df = 1, F = 44.818, Group and the Control Group had participated in the previously p < 0.05). The elderly walk longer and use anti-slip devices more mentioned information meetings.) frequently.

Fig. 1. The number of respondents completing Questionnaires I and II. 1202 G. Berggård, C. Johansson / Accident Analysis and Prevention 42 (2010) 1199–1204

Table 1 Exposures: total walking times and total walking distances.

Characteristics Group

Intervention Control Comparison Total

Mean daily total walking distance (km) 2.95 (N = 919) 2.85 (N = 1093) 2.77 (N = 451) 2.87 (N = 2463) Mean daily total walking time (min) 32 (N = 919) 33 (N = 1094) 37 (N = 446) 33 (N = 2459) Total walking distance (km) 2714 3099 1247 7061 Group share of total distance (%) 38 44 18 100

Nearly all respondents from the Intervention Group, or 86%, Respondents experiencing incidents or falls had a significantly used an anti-slip device at least at one occasion during the trial reduced mean daily walking distance with anti-slip devices during period (see Table 3). Everybody in this group had been supplied the day on which the incident or fall occurred compared with the with one device. Some respondents from the other groups, 35% mean daily walking distance when using anti-slip devices with- from the Control Group and 31% from the Comparison Group, used out having any incidents or falls (see Table 4). The mean total an anti-slip device they had acquired before the start of this project daily walking distance for anti-slip users with anti-slip devices at least at one occasion during the trial period. Access to anti-slip without incidents or falls was 3.75 km and with incidents or devices in the Intervention Group resulted in more frequent usage falls 2.12 km. The slip/fall interrupted the trip and reduced the of anti-slip devices. The respondents in the Intervention Group distance. accounted for 59% of anti-slip usage, and 80% of trips with anti-slip devices were made by people in the Intervention Group. Access to 3.4. Analysis of reports on incidents or falls (Questionnaire III) anti-slip devices increases the number of trips and also the length of the trips. It should be noted that 55 of the 64 incidents/falls occurred × Anti-slip devices were used during 356 person days: 284 per- without anti-slip devices. Only 9 incidents or falls occurred with × son days in the Intervention Group, 52 days in the Control Group anti-slip devices, while six actual falls occurred when not using and 20 days in the Comparison Group. In total 14% of the reported anti-slip devices and one when using an anti-slip device. None of days were with anti-slip devices, and 14% of the slips occurred on the falls resulted in an injury. days when anti-slip devices were used. There was no statistically significant difference in the number There were no statistical significant differences between mean of incidents or falls or actual falls between the days when anti-slip daily total walking distances for respondents experiencing inci- devices were used or days without the devices (Fishers exact test, dents or falls compared with respondents not experiencing Chi-square test). Of the nine incidents or falls with anti-slip devices incidents or falls within any of the three groups. There were no were foot-blade devices used in two cases and heel devices were statistical significant differences between age groups for incidents used in four cases. In the other cases the types were not reported. or falls, with 33 of the incidents or falls occurring among the Winter shoes were used in 56 incident or fall cases. Other shoes younger respondents (younger than 45 years) and 31 among the were used in nine cases, five of which were with ordinary shoes. 49 older respondents (45 years or older). of the incidents or falls took place during daylight.

Table 2 Exposure for respondents using anti-slip devices compared with respondents not using them.

Characteristics Group

Intervention Control Comparison Total

Mean daily total walking distance for respondents during days when using anti-slip 3.68 6.51 3.55 4.08 devices (km) Number of days with walking trips for respondents with anti-slip devices 284 52 20 356 Mean daily walking distance when using the anti-slip devices (km) 3.36 5.88 3.15 3.71 Share of winter days with walking trips with anti-slip devices (%) 80 15 5 100 Total walking distance during days when using anti-slip devices (km) 953 305 63 1321 Share of total walking distance with anti-slip devices (%) 72 23 5 100

Mean daily total walking distance for respondents NOT using anti-slip devices (km) 2.63 2.65 2.73 2.66 Number of days with walking trips for respondents NOT using anti-slip devices 635 1041 431 2107 Share of winter days with walking trips NOT using anti-slip devices (%) 30 49 21 100 Total walking distance during days when NOT using anti-slip devices (km) 1670 2761 1177 5608

Share of days with walking trips with anti-slip devices compared with all days with 31 5 4 14 walking trips within each group (%)

Table 3 Anti-slip usage and occurrence of incidents or falls among respondents.

Characteristics Group

Intervention Control Comparison Total

Respondents using walking diaries 22 23 16 61 Total no. of reported walking days 1028 1138 492 2658 Respondents reporting incidents or falls 9 13 6 28 Respondents using anti-slip devices 19 8 5 32 Number of incidents or falls 29 23 12 64 Incidents or falls per day 0.028 0.020 0.024 0.024 Incidents or falls per respondent 1.318 1.000 0.750 1.049 G. Berggård, C. Johansson / Accident Analysis and Prevention 42 (2010) 1199–1204 1203

Table 4 Mean daily walking distance with anti-slip devices compared with experiences of incidents or falls.

Variable Group

Intervention Control Comparison Total

Mean daily walking distance using anti-slip devices with incident or fall (km) 1.78 (N = 8) 4.80 (N =1) –(N = 0) 2.12 (N =9) Mean daily walking distance using anti-slip devices without incident or fall (km) 3.40 (N = 276) 5.90 (N = 51) 3.15 (N = 20) 3.75 (N = 347)

Table 5 There are statistical differences in mean total daily walking dis- Relative incident or fall rate and actual fall rate on days when using or not using tance between using and not using anti-slip devices in our study anti-slip devices. (df=1,F = 86.139, p < 0.05) (see Table 5). Access to anti-slip devices Anti-slip improves walking mobility during the wintertime. Especially in the Users Non-users Total Control Group the mean daily walking distance when using anti- slip devices is twice as long as long as the average walking distance No. of days 356 2107 2463 Mean daily walking distance (km) 4.08 2.66 2.87 all year round in Sweden in general, 2–3 km. Total walking distance (km) 1453 5607 7061 Users of anti-slip devices experienced 6.2 incidents per 1000 km Number of incidents or falls 9 55 64 of walking. Non-users experienced 9.8 incidents per 1000 km of Incident or fall per day 0.025 0.026 0.026 walking. The incidence rate ratio is 0.63, suggesting a protective Incident or fall per km 0.0062 0.0098 0.0090 effect of the anti-slip devices. However, the difference is not statis- Actual falls 1 6 7 Fall per km 0.00069 0.00107 0.00099 tically significant (t = 1.47 in t-test based on Poisson assumption), and with the 95% confidence interval of the incidents 6.2 ± 4.1 for users and 9.8 ± 2.6 for non-users. The surface was packed snow in 17 (26%) cases, loose snow/slush The rate of falls was 0.69 per 1000 km of walking for users of in 13 (20%) cases, thin ice in 10 (15%) cases and thick ice in 23 (35%) anti-slip devices and 1.07 per 1000 km of walking for non-users. cases. The ice/snow surface had no loose snow in 29 (45%) cases. The The rate ratio is 0.64, again suggesting a protective effect of the anti- surface was covered with loose snow in 24 (37%) cases. In one case slip devices. However, the difference is not statistically significant the surface was covered with sand and in three cases with gravel. (t = 0.46 in t-test based on Poisson assumption) and with the 95% ± ± The local climate was dry/fair in 47 (72%) cases and snowfall only confidence interval of the falls 0.69 0.45 for users and 1.07 0.31 occurred in 12 (19%) cases. There was no wind in most of the cases for non-users. reported. 47 of all the 58 slips and falls were estimated temperature It should be noted that both incidents and falls were events that was reported occurred in temperatures between −6Cand0C. did not result in personal injury. There were no significant differences in the relation incidents or falls per walking day for those who used anti-slip devices, 0.025, 3.5. Experiences of using anti-slip devices (Questionnaire IV) and those who did not, 0.026. In other words, an increased mean daily total walking distance, caused by using anti-slip devices, did 75% respondents reported good or very good balance on ice. not increase the number of incidents or falls. 100% reported good or very good balance on snow. 60% reported The respondents experienced 57 incidents and 7 falls during no problems/no critical situations on ice. 75% reported no critical the study period. Both the slip and fall rate per km was 50% lower situations on snow. As examples of critical situations on ice two among anti-slip users compared to non-users. Most of the slips or respondents reported problems with snow on ice. As example of falls occurred in daylight and in the temperature range of −6 ◦Cup critical situations on snow one respondent reported problems with to 0 ◦C. snow attached between the shoe and parts of the device. All stated The risk of any kind of single-pedestrian injury is that they will continue to use anti-slip devices and recommend 0.000345/walking-km in Sweden (Gustafsson and Thulin, 2003). their friends to do so also. This figure includes all single-pedestrian injuries all year round. Slip and fall accidents on snow and ice are probably the largest 4. Conclusions and discussion part of that figure, with 2–3 people per 1000 inhabitants expected to be injured on snow or ice every year in Sweden. The exposure 50% of the respondents stated that they had previous experi- when walking on snow and ice is a minor part of the total exposure ences of using anti-slip devices; at least at one occasion, often but because these conditions occur only during a part of the year. Half not always or always. The respondents had experienced 24 falls of the slip and fall accidents occur on snow and ice and occur during previously during the winter 2007/2008. Two of the falls occurred one third of the year. The risk of a fall injury on snow and ice can when using an anti-slip device. be expected to be in the magnitude of five to ten times the average In total 52% of the respondents used anti-slip devices in at least risk of a single-pedestrian injury on uncovered ground (Wallman one occasion in this study. A larger portion, 86%, of the respondents et al., 1997). A comparison between this figure based on a national in the Intervention Group (all of them were equipped with anti-slip estimate and the study conducted here shows that when using devices by us) used anti-slip devices compared to 36% in the Control anti-slip devices the fall rate is 1.8 times the uncovered-ground Group and 31% in the Comparison Group. The respondents in the risk of a single-pedestrian injury and when not using an anti-slip Control and the Comparison Groups used anti-slip devices of their device the fall rate is 2.8 times the uncovered-ground risk of a own. Information about the risk of slipping and falling to the Control single-pedestrian injury. Group did not promote the usage of anti-slip devices compared to In the study of fall-prone elderly the slip-per-trip rate was the Comparison Group. Access to anti-slip devices increases the 0.063/trip (N = 3634) for anti-slip users and almost twice that, usage of anti-slip devices. 0.113/trip (N = 4274), for ordinary winter shoe users. (The distances The mean daily total walking distance among all of the respon- of the trips were not recorded.) The relationship between falls and dents in this study is similar to the average walking distance slips was 0.56 for anti-slip users and 0.89 for winter shoe users. The according to the Swedish National Travel Survey, which is 2–3 km relationship between injuries and falls was 0.04 for anti-slip users (SIKA Statistics, 2007). and 0.23 for winter shoe users. This gives a relationship between 1204 G. Berggård, C. Johansson / Accident Analysis and Prevention 42 (2010) 1199–1204 injuries and slips of 0.003 for anti-slip users and 0.021 for winter Björnstig, U., Björnstig, J., Dahlgren, 1997. Slipping on ice and snow—elderly women shoe users (McKiernan, 2005). and young men are typical victims. Accident Analysis and Prevention 29, 211–215. Both that study and our study indicate a reduction in fall rate Elvik, R., 2000. The consequences of better winter road maintenance for pedes- by using anti-slip devices. Therefore this study indicates that the trians and bicyclists. In: Proceedings from Via Nordica, June 13–16, 2000 (in exposure can increase without increasing the risk of slips or falls. Norwegian). Elvik, R., Vaa, T., 2004. The Handbook of Road Safety Measures. Elsevier, Oxford, UK, Our study is limited to 67 respondents in the ages 27–67 years. In ISBN: 0-08r-r044091-6. Sweden 3/1000 inhabitants annually is expected to need medical Gard, G., 2000. Prevention of slips and fall accidents: risk factors, methods and treatment of an injury from a fall accident on icy or snowy surfaces. suggestions for prevention. Physical Therapy Reviews 5, 175–182. No such injury was recorded in our study. The relations between Gard, G., Berggård, G., 2006. Assessment of anti-slip devices from healthy individuals in different ages walking on slippery surfaces. Applied Ergonomics 37, 177–186. injuries from falls and the exposure are not known. A larger age Gard, G., Lundborg, G., 2000. Pedestrians on slippery surfaces during span and a larger group of respondents are needed to verify our winter—methods to describe the problems and practical tests of anti-slip findings. Further studies of wintertime exposure and slip or fall devices. Accident Analysis & Prevention 32, 455–460. Gard, G., Lundborg, G., 2001. Test of anti-slip devices on five different slippery sur- occurrence, and the relation to injuries, are needed to give access to faces. Accident Analysis & Prevention 33, 1–8. better data on risk for pedestrians comparable with vehicle-related Gustafsson, S., Thulin, H., 2003. Pedestrians and Cyclists – Exposure and Injury Risks data. in Different Traffic Environments for Different Age Groups. Results from TSU92 – the Years 1998 to 2000. VTI meddelande 928, Linköping, Sweden (in Swedish). The study indicates that by using appropriate anti-slip devices Hara, F., Akitaya, E., Suda, C., Morita, S., 1997. Study on measures used by women and having information about when and where to use them, based in walking in wintertime. In: Izuma, M., Nakamura, T., Sack, R.L.A.A. (Eds.), Pro- on their design, people will avoid having slips and falls. The number ceedings of the Third International Conference on Snow Engineering in Sendai, Japan. May 26–31, 1996: Snow Engineering: Recent Advances. Balkema, Rotter- of respondents experienced in using anti-slip devices will continue dam/Brookfield, pp. 411–414. to grow, as will the number recommending others to use these Juntunen, P., Grönqvist R., Mattila S., Aschan C., Hirvonen M., 2005. Does anti- devices. Therefore, further studies on the use of, and the benefits skid devices and studded footwear increase safety during slippery outdoor of using, anti-slip devices are recommended. This will enable us to activities? (Pilot study). In: Abstracts from Nordiska olycksforskarseminariet, NoFS XVI, Gilleleje, Denmark/8 – 10.6.2005. Available at: http://www. compare the reduction of risk achieved by providing and advocating sifolkesundhed.dk/upload/abstracts nofs 001.pdf (accessed November 15, the use of anti-slip devices with other risk reduction measures. 2007). By reducing the risk of a slip and fall accident during winter- Juntunen, P., Grönqvist, R., 2006. With anti-slip devices and shoes equipped with studs you can stay on your feet on slippery surfaces during wintertime, the number of single-pedestrian accidents can be reduced, time. Available at: http://www.ttl.fi/Internet/Svenska/Informationsformedling/ thus improving pedestrian safety in the traffic environment. Pressmeddelanden/Arkiv/2005/press 29 05.htm (updated January 3, 2006) (accessed November 15, 2007) (in Swedish). Lindmark, M., Lundborg, G., 1987. Maintenance and Operation of Footways Dur- Acknowledgements ing Winter Time. Swedish Association of Local Authorities (SALA), Report 11, Stockholm (in Swedish). McKiernan, F.E., 2005. A simple gait-stabilizing device reduces outdoor falls and This study was financed by the Department of Civil, Mining and nonserious falls in fall-prone older people during winter. Journal of American Environmental Engineering, Luleå University of Technology. The Geriatric Society 53, 943–947. authors would like to acknowledge Dr. Karin Brundell-Freij, Dr. Nilsson, G., 1986. Slip Accidents. VTI Rapport 291, Linköping (in Swedish). Nordin, H., 2003. Slip Accidents on Snow and Ice. Short Accident Facts. Swedish Data Anders Lagerkvist, Dr. Lars Leden and Dr. Per Gårder for valuable From EHLASS–EU System for Monitoring of Home- and Recreation Accidents, comments on drafts of this manuscript. 1:2003. The Swedish Consumer Agency (in Swedish). Öberg, G., Nilsson, G., Velin, H., Wretling, P., Berntman, M., Brundell-Freij, K., Hydén, C., Ståhl, A., 1996. Single Accidents Among Pedestrians and Cyclists. VTI medde- References lande 799, Linköping, Sweden. ISSN: 0347-6049 (in Swedish). SIKA Statistics, 2007. SIKA Statistics 2007:19, Communication Patterns – RES Berntman, M., 2003. Consequences of traffic casualties in relation to traffic- 2005–2006, The National Travel Survey. Swedish Institute for Transport and engineering factors. An analysis in short-term and long-term perspective. Communication Analysis. Doctoral Thesis. Bulletin 214. Department of Technology and Science, LTH, Lund. Wallman, C.-G., Wretling, P., Öberg, G., 1997. Effects of Winter Road ISBN: 91-88292r-r03-04. Maintenance—State of the Art. VTI Rapport 423A, Linköping, Sweden.