The Effect of Differing Traffic Volumes on Sleep Related Crashes
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1111 Lo~;~ghb.orough V Umverstty •· .. ,· University Library Author/Filing Title ......... f.~~:T..L:-.~1. ............................ Class Mark ..................... T. .......................................... Please note that fines are charged on ALL overdue items. A FIELD STUDY OF SLEEP RELATED ROAD CRASHES by Diane Flatley j / A Master's Thesis Submitted in partial fulfilment of the requirements for the award of Master of Philosophy of Loughborough University March2004 © by Diane Flatley 2004 Class 1------·----1Ace No. ·.-. This Thesis is dedicated to my Mum and Dad and to my husband David ii ABSTRACT This study is an assessment of the incidence of Sleep Related Crashes (SRCs) on different roads and different road types. There is no roadside methodology available to 'test' for driver sleepiness and there is no UK system in place for the reporting of crashes caused by driver sleepiness. Accident statistics announced by the Govermnent are dependent upon STATS19, a data collection system that is not required by law, and does not record causation factors. Police collision report forms vary from force to force, with few recording causes. Police officers are not trained to attribute crashes to driver sleepiness. SRCs are, therefore, under-reported. Using established criteria, this thesis presents findings from in-depth analysis of over 2,000 police files on Road Traffic Crashes (RTCs) which occurred on 17 sections of roads of differing classification and with different characteristics. Files were studied for causation factors, and data is presented on severity, sex and age, occupation, vehicles involved, location, and time of day, week and month. Data were analysed to compare and contrast different road types, urban and rural roads, and the effect of differing traffic density, and natural and artificial lighting. Overall, 18% of all RTCs resulting in death or injury were caused by driver sleepiness, and 18% ofall fatal crashes were sleep related. SRCs were more evident on motorways than on non-motorway roads (20% and 14% respectively) and the difference between these proportions was significant. However, these are conservative proportions given that crashes attributed by the police to other causation factors such as tyre blowouts and manoeuvre error may also be caused by drivers falling asleep at the wheel. Approximately half of all crashes between midnight and 0600h were caused by driver sleepiness and almost all (83%) of fatal crashes occurring between 0400-0600h were sleep related. The difference between the proportions of SRCs and RTCs occurring between 0000-0600h was highly significant. However, SRCs were distributed evenly over the 24h period in absolute terms. 68% of SRCs were attributed to car drivers, over one third of drivers in SRCs drove for a living, and almost half of all SRCs were single vehicle crashes. Most SRCs (83%) involved male drivers, and over one third, men s;30y, iii ---- - - ------------------------------- especially during the night and early hours of the morning. Older men and women had crashes later in the day and during the afternoon. Almost half of SRCs involving women occurred during 0800-l400h. Young women drivers aged S30y caused 67% of SRCs on non-motorway roads compared to 35% for all crashes and 39% for SRCs on motorways. 7% of men possible or probably causing SRCs on non-motorway roads were 71y or older. The effectiveness of artificial lighting in reducing road crashes is questionable. Analysis of a subset of data showed only a marginal reduction of RTCs when roadside lighting is present. This was also true for the proportion of RTCs that were SRCs. There was a significantly greater proportion of SRCs during natural daylight than darkness (0530· 0730h). The effect of traffic flow on the number of crashes (all causes) and SRCs showed a trend. As Annual Daily Traffic Flow increased with each of the different sections of roads, the number of RTCs and SRCs also increased. This is true for the proportion of crashes that were SRCs on the non-motorway roads. However, the opposite was true for motorways. Research shows that SRCs are more likely to occur on motorways and although this study supports this, interestingly, SRCs as a proportion of RTCs were reduced on motorways with high traffic flows. This study also shows that SRCs on non-motorway roads occurred with some clustering of crashes on certain sections of roads. Furthermore, SRCs on non-motorways were more likely to result in fatal or serious injuries than on motorways. Hence, drivers need to be aware of the dangers of driving whilst sleepy on non-motorway roads as well as motorways. There needs to be a greater public awareness of driver sleepiness and the dangers of driving whilst sleepy, for all drivers and for all those concerned with driving. iv ACKNOWLEDGEMENTS My appreciation and thanks to Professor Jim Home for his support, guidance and supervision. My thanks to Dr Louise Reyner for her encouragement, support and supervision, and to my colleagues at the Sleep Research Centre for their encouragement. I gratefully acknowledge the Department for Transport and Bryant Homes Limited for funding this research. My thanks to the following constabularies for allowing access to their files: Gloucestershire Constabulary, Kent County Constabulary, Lincolnshire Police, West Mercia Constabulary, Northamptonshire Police, North Yorkshire Police, Staffordshire Police and Warwickshire Constabulary. Thank you to the police officers and staff at the police Administration and Process units for their friendly assistance. I gratefully acknowledge W. S. Atkins Transportation Engineering, Babtie, Capita DBS, Lincolnshire County Council, Mouchel Consulting Limited, Optima Infrastructure Management, for traffic flow data and road characteristics. Thanks also to· Systems Options Ltd for provision of and assistance with the mapping operating system and software, and to the GIS Unit, Office of the Deputy Prime Minister and DIT for mapping tiles, copyright Ordnance Survey. Finally, I would like to thank my family. Thank you to my daughter Holly for her patience, to my son Owen for his encouragement, and, a big thank you to my husband David for his endless patience, understanding and support. V CONTENTS Abstract iii Acknowledgements V Table of Contents vi CHAPTER!: THE NATURE OF THE PROBLEM 1 1.1 ROAD TRAFFIC CRASHES 1 1.2 SLEEP RELATED CRASHES- THE COST 2 1.3 HIGH PROFILE CRASHES CAUSED BY 3 DRIVER SLEEPINESS 1.4 SLEEP RELATED CRASHES AND CRASH TYPE 4 1.5 CRASHES ANALYSED BY VEHICLE TYPE 5 1.6 SEVERITY OF CRASHES 6 1.7 TIME OF DAY EFFECTS 7 1.8 DAY OF WEEK AND MONTH PATTERNS 8 1.9 CHARACTERISTICS OF THE DRIVER 9 1.9.1 Sex and Age of Driver 9 1.9.2 Occupation 9 1.10 AIMS AND OBJECTIVES OF THIS RESEARCH 10 CHAPTER2: CRITIQUE OF EXISTING METHODOLOGIES 11 2.1 SURVEYS/QUESTIONNAIRES 11 2.1.1 Population Survey 12 2.1.2 Roadside Survey 12 2.1.3 Postal Questionnaire 13 2.1.4 Telephone Surveys 13 2.1.5 Survey of roads 14 2.2 NATIONAL DATABASES 14 2.3 DRIVER SIMULATOR STUDIES 15 2.4 MOTOR VEHICLE DRIVING ON ROADS 16 AND TRACKS 2.5 POLICE RECORDS 16 VI 2.5.1 UK collection of police data on 18 Road Traffic Crashes/STATS19 CHAPTER3: OVERVIEW OF ROAD TYPES STUDIED 23 3.1 CLASSIFICATION OF ROADS 23 3.2 CRASHES ON DIFFERENT ROAD TYPES 24 3.2.1 Urban and Rural Roads 25 3.2.2 Artificial and Natural Lighting 26 3.2.3 Traffic Density 26 CHAPTER4: METHODOLOGY 27 4.1 DESIGN 27 4.2 DATA COLLECTION 28 4.2.1 Police files 28 4.2.2 Traffic Flow Data 30 4.2.3 Severity of Crashes Causing Death or Injury 31 4.3 DATA ANALYSIS 32 4.3.1 Criteria for Sleep Related Crashes 32 4.3.2 Computer Software 33 CHAPTERS: RESULTS 34 5.1 CAUSATION 34 5.2 VEHICLES INVOLVED 37 5.2.1 Vehicle Type 37 5.2.2 Vehicle Type and Time of Day 38 5.2.3 Single Vehicle Crashes 40 and Multiple Vehicle Crashes 5.3 SEVERITY AND NUMBER OF CRASHES 41 5.4 TIME OF DAY/WEEK/MONTH 42 5.4.1 TimeofDay 42 5.4.2 Time of Day and Severity ofinjuries 43 5.4.3 DayofWeek 45 5.4.4 Month/Season 46 5.5 CHARACTERISTICS OF THE DRIVER 48 5.5.1 Sex and Age 48 vii 5.5.2 Sex and Time of Day 50 5.5.3 Sex and Age and Time of Day 52 5.5.4 Occupation 54 5.6 LOCATION 55 5.7 DISCUSSION 62 5.8 KEY POINTS 67 CHAPTER6: COMPARISON OF DIFFERENT ROAD TYPES 69 6.1 CAUSATION 69 6.2 VEHICLES 71 6.2.1 Vehicle Type 71 6.2.2 Single Vehicle Crashes 72 and Multiple Vehicle Crashes 6.3 SEVERITY AND CASUALTIES 74 6.4 TIME OF DAY/WEEK/MONTH 77 6.4.1 TimeofDay 77 6.4.2 DayofWeek 78 6.4.3 Month/Season 80 6.5 CHARACTERISTICS OF THE DRIVER 82 6.5.1 Sex and Age 82 6.6 DISCUSSION 84 6.7 KEY POINTS 85 CHAPTER 7: THE EFFECT OF NATURAL AND ARTIFICIAL 87 ROADSIDE LIGHTING ON SLEEP RELATED CRASHES 7.1 INTRODUCTION 87 7.1.1 Casualties 89 7.2 EFFECT OF ARTIFICIAL LIGHTING 89 7.2.1 Method 89 7.2.2 Results 90 7.3 EFFECT OF NATURAL LIGHT 93 7.3.1 Method 93 7.3.2 Results 94 7.4 DISCUSSION 94 viii 7.5 KEYPOINTS 95 CHAPTERS: THE EFFECT OF DIFFERING TRAFFIC VOLUMES 97 ON SLEEP RELATED CRASHES 8.1 INTRODUCTION 97 8.2 METHOD 98 8.3 RESULTS 99 8.3.1 2h Traffic Flows 99 8.3.2 Road Traffic Crashes/ 100 Sleep Related Crashes and Traffic Flow 8.3.3 RTCs/SRCs and Traffic Flow lOO By Time of Day 8.3.4 RTCs and SRCs in relation to 101 mean traffic movement 8.3.5 RTCs and SRCs per mile per year 102 8.3.6 Early Morning Traffic Flows 105 8.3.7 24h Traffic Density and Sleep Related Crashes 107 as a Proportion of all Crashes 8.4 DISCUSSION 109 8.5 KEY POINTS 109 CHAPTER 9: MAIN DISCUSSION 111 FURTHER RESEARCH !20 REFERENCES 122 APPENDICES 133 Appendix 1: DESCRIPTION OF ROADS 133 Appendix 2: DATA COLLECTION FORM 153 Appendix 3: STATISTICAL SIGNIFICANCE 156 ix CHAPTER!: THE NATURE OF THE PROBLEM 1.1 ROAD TRAFFIC CRASHES Road Traffic Crashes (RTCs) constitute one of the major problems of modem daily life.