VIII међународна конференција VIII International Conference Безбедност саобраћаја у локалној заједници RAOD SAFTY IN LOCAL COMMUNITY Ваљево, Хотел Дивчибаре, Valjevo, Divcibare Hotel, 18 – 20. април 2013 April 18- 20, 2013.

656.025.2.08(497.5)

TRAFFIC SAFETY INDICATORS FOR URBAN PUBLIC TRANSPORT

ČIMBENICI SIGURNOSTI U JAVNOM GRADSKOM PRIJEVOZU

Davor Brčić1, Marko Slavulj2, Dino Šojat3, Daniela Bolčević Turčić4

Abstract: Statistical monitoring of different characteristics of traffic accidents through period of several years is a valuable indicator of certain patterns which can greatly serve for identifying causes of traffic accidents. Paper will be based on processing of traffic accidents database regarding bus traffic of local city public transport operator (ZET – Electric Tram). Also, the paper will analyze traffic accidents according to their: location, time characteristics, characteristics within bus transit network and occurrence by bus transit lines. The aim of this paper is to perform a statistical analysis of traffic accidents which will be used to determine the degree of risk of all factors in traffic (human, vehicle and environment), and to define necessary measures to increase safety of urban public transport. Key words: traffic accident, traffic safety, bus transit, time period, City of Zagreb

Sažetak: Statističko praćenje raznih značajki prometnih nesreća kroz duža vremenska razdoblja je važan pokazatelj zakonitosti koje uvelike mogu poslužiti pri utvrđivanju njihovih uzroka. Rad je zasnovan na obradi podataka o prometnim nesrećama u autobusnom prometu Grada Zagreba, pod nadležnošću ZET-a (ZET – Zagrebački električni tramvaj) kao lokalnog prijevoznika. Također će se u radu analizirati prometne nesreće prema lokaciji, vremenskim značajkama, značajkama unutar mreže autobusnih linija i učestalošću na pojedinačnim linijama. Cilj rada je provedba statističke analize prometnih nesreća koja bi utvrdila stupanj sigurnosti u prometu prema čimbenicima sigurnosti (čovjeku, vozilu i okolini), kako bi se odredile mjere za povećanje sigurnosti u javnom gradskom prometu. Ključne riječi: prometna nesreća, sigurnost u prometu, javni autobusni prijevoz, vremensko razdoblje, Grad Zagreb

1. INTRODUCTION

Traffic safety is an essential characteristic of every transportation system, especially the public transport as a sustainable passenger transit mode. This is because reliability of public transport has to be its top priority, resulting in better regularity and punctuality and eventually better efficiency. Traditional understandings of safety in public transport include five groups of factors in the environment of those same factors (Cerovac, 2001): -- human factors (considering bus drivers, passengers or pedestrians), -- roads (pavement status, lighting quality, weather conditions), -- vehicles (technical capabilities, roadworthiness), -- network traffic flows, -- random factors, characterized by erratic and unexpected occurrence – such of those are sudden changes on infrastructure or sudden weather condition changes. Environment characteristics have a great impact on traffic safety because they mostly influence human factors through human perception. 1 Prof. Davor Brčić, Ph.D., Faculty of Transport and Traffic Sciences, Vukelićeva 4, 10000 Zagreb, , [email protected] 2 Marko Slavulj, Ph.D. Candidate, Faculty of Transport and Traffic Sciences, Vukelićeva 4, 10000 Zagreb, Croatia, [email protected] 3 Dino Šojat, mag. ing. traff., Ljerke Šram 2, 10000 Zagreb, Croatia, [email protected] 4 Daniela Bolčević Turčić, mag. ing. traff., Student, Zagrebacki Holding Co., Department “ZET”, Ozaljska 105, 10000 Zagreb, Croatia, daniela_ [email protected]

143 Davor Brčić, Marko Slavulj, Dino Šojat, Daniela Bolčević Turčić TRAFFIC SAFETY INDICATORS FOR URBAN PUBLIC TRANSPORT

The increase in number of road vehicles in the City of Zagreb is continously changing traffic safety, so it needs to be constantly monitored. Likewise, each irregularity has a negative influence on every participant. The aim of this paper is to perform a stastical analysis of traffic accidents in purpose of determining the level of safety of bus transit network of ZET and suggesting measures which would increase safety of bus transit in the City of Zagreb.

2. METHODOLOGY

Although traffic safety as a characteristic of transportation system is generally highly complex in nature, the most suitable way to describe it is by direct and indirect factors. Direct factors include data about traffic accidents and their consequences. Indirect factors include e.g. usage of seat belts, number of intoxicated drivers, speeds of other vehicles in the bus transit network, influence of drivers’ age, business hours or working experience. Data regarding traffic accidents was gathered by processing yearly traffic accident reports of ZET. In this paper the analyzed data included the number of traffic accidents relative to time, number of vehicles or distance. In such manner traffic accident is defined as an event in which at least one vehicle took part, and at least one person died or was injured, or material damage was caused. Statistical monitoring of traffic accidents through long periods of time is a very good indicator of relations which can serve greatly to recognize traffic accident causes. The methods that were used for data analysis include analysis and synthesis method, descriptive method and statistical methods (e.g. the linear regression method for the purpose of analysis of yearly changes in number of traffic accidents).

3. RESEARCH RESULTS

The research results are divided into three groups: a general overview of bus traffic safety, an analysis of traffic accidents according to specific time periods (time-based analysis) and an analysis of traffic accidents according to spatial characteristics (space-based analysis).

3.1 General overview of bus traffic safety

Information about bus transit network is given in Table 1, which shows an average number of 233 buses operating and an average number od 27 milion vehicle kilometers crossing per year in the period from 2001 to 2011. During the past two years the number of buses operating on network has increased by appoximately 15%, accompanied by an equivalent increase in vehicle kilometers crossed, which resulted in constant number of kilometers crossed by a single bus on annual basis. Bus transit network is positioned along city’s road network (on avenues, and side streets). The ratio of bus reserved lanes (yellow lanes) is less than 1%, making bus transit network completely under influence by other traffic flows in road network.

Table 1. An overview of average number of buses, vehicle kilometers crossed and level of motorization in Zagreb during the period from 2001 to 2011 Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Average number of buses 228 227 226 226 226 222 229 222 232 263 257 Number of vehicle kilometers crossed per year 26,5 26,1 26,1 26,0 26,0 25,6 26,3 27,1 28,7 29,5 28,5 Level of motorization, vehicles per 1000 citizens 388 406 430 450 469 490 508 525 516 506 497

Table 1 also shows the level of motorization in the City of Zagreb for the same period of time (data was gathered from yearly statistical reports of the City of Zagreb), which shows growth until 2008, followed by decreasing trend up to the present day. At global scale, level of motorization is under the influence of: -- increase of the citizens’ purchasing power leading to increase of traffic volume, reaching its maximum in 2008, -- the world’s global financial crisis, which has reduced citizens’ purchasing power after 2008. -- According to ZET, traffic accidents are classified into 3 groups: -- allisions (bus with another bus, bus with tram, bus with a motor vehicle and bus with a fixed road object), -- collisions (bus with another bus, bus with a motor vehicle, bus with tram and bus with a bicycle or motorcycle),

144 VIII Meђународна конференција БЕЗБЕДНОСТ САОБРАЋАЈА У ЛОКАЛНОЈ ЗАЈЕДНИЦИ Ваљево, Хотел Дивчибаре, 18 – 20. април 2013

-- other accidents (bus derailment, bus overturning, bus-pedestrian accident, passengers’ falling inside a bus, fixed road object crash and unclassified accidents5).

Figure 1. Absolute number of traffic accidents in bus transit network during the period from 1996 to 2011

Accidents with the largest share in the absolute number are allisions of bus with motor vehicle (49%), collisions of bus with motor vehicle (29%) and passengers’ falling inside a bus (8%). Accidents that appear more frequently but less than 5% of all accidents are allisions of bus with a fixed road object, fixed road object crashes and unclassified accidents. Such values are a natural consequence of traffic flow structure in the road network used by buses in which the number of private cars has the biggest share as well as relatively frequent occurance of traffic incidents accompanied by sudden braking. Figure 1 shows the absolute number of traffic accidents in bus transit network during the period from 1996 to 2011. The following changes can be noticed: a slight increase in number of traffic accidents at the end of 1990s, a sudden drop to 283 accidents in the year 2000, a more prominent growth until 2007 when it reaches its maximum of nearly 500 accidents and finally a sudden drop up to the present day.

Figure 2. Relative number of traffic accidents in the past 10 years

The relative number of traffic accidents6 (Fig. 2) describes safety more accurately. This is because it doesn’t depend on number of operating vehicles. Figure 2 shows that changes of absolute and relative number of accidents occur in a similar manner. Two interesting time intervals were analyzed (before and after traffic accident maximum) and linear regression was performed on those intervals. It showed that relative number of accidents grew by 0,086 accidents per 100.000 km yearly with a correlation coefficient of 0,84 (strong correlation) before 2007, and after 2007 it fell by 0,156 accidents per 100.000 km yearly with a correlation coefficient of 0,95 (very strong correlation). Therefore the relative number of traffic accidents is subject to similar changes like the level of motorization in Table 1, indicating that the relative number of traffic accidents depends on level of motorization of road network in the City of Zagreb. This confirms traditional relations: traffic volume is dependant on level of motorization and relative number of traffic accidents is dependent on traffic volume.

5 Unclassified accidents include cyclists’ stumbles, tire damaging, window breakings, damaging caused by unknown persons, stumbles on objects dropped from another vehicles etc. 6 The relative number of traffic accidents is the absolute number of traffic accidents divided by the total number of vehicle kilometers crossed, measured in accidents per 100.000 km

145 Davor Brčić, Marko Slavulj, Dino Šojat, Daniela Bolčević Turčić TRAFFIC SAFETY INDICATORS FOR URBAN PUBLIC TRANSPORT

Table 2. Average number of accidents per day and per vehicle during the period from 2001 to 2011 Year 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Average accidents per day 0,94 0,98 0,87 1,05 1,13 1,06 1,36 1,24 1,34 1,20 0,94 Average yearly number of accidents per bus 1,51 1,58 1,41 1,70 1,82 1,74 2,17 2,04 2,10 1,67 1,33 For the purpose of describing safety in a more suitable way (for passengers), average number of accidents per day and average yearly number of accidents per bus can be proposed (Tab. 2). Since the daily number of vehicle kilometers crossed by buses is about 74.000 km, it is expected to happen 1.1 traffic accidents per day and 1.73 accidents per bus during one year.

3.2. Analysis of traffic accidents according to specific time periods

Analysis of traffic accidents in relation to time considers the influence of specific factors during the characteristic time intervals. Traffic accident data are presented as percentages in whole time period observed which is periodically repeated. In this paper those time intervals were days during a week and two-hour intervals during a day. The data gathered from ZET was analyzed for the period from 2004 to 2011, and was turned to average annual level. Although the data obtained from ZET had the absolute number of traffic accidents only, time intervals with the similar number of vehicle kilometers can serve for comparison.

Figure 3. Percentages of absolute number of traffic accidents, days during a week By looking at the percentage of traffic accidents by days of the week (Fig. 3), relation to traffic volume during workdays and weekend can be observed. Like in most traffic-based systems, the highest percentage of traffic accidents is recorded on Mondays and Fridays just like traffic volumes are highest during those days. That pattern of traffic volumes is due to maximum difference in traffic volumes from Friday to Saturday and from Sunday to Monday which occurs because people have tendency to migrate on a larger scale between work weeks and weekends. Tuesday, Wednesday, and Thursday are usually relevant for safety assessment during work week. If relative number of traffic accidents was considered, safety would still be under the influence of traffic volume in the road network. When observing the absolute number of traffic accidents during a day (Fig. 4), it can be easilly noticed that the maximum number of traffic accidents happens during the afternoon peak hour. Although the morning peak hour in Zagreb is more intense than the afternoon peak hour, it is shorter in time, so the probability of a traffic accident occurence depends more on duration but less on traffic flow intensity. In the past decade road network of the City of Zagerb is constantly under the pressure of traffic flows, even in the time periods between morning and afternoon peak hours, so the number of traffic accidents isn’t much less than is during the afternoon peak hours. Number of vehicle kilometers crossed in the evening periods is much smaller, so the absolute and relative number of traffic accidents is substantially lower, but tipically with higher consequences (during periods without daylight).

Figure 4. Percentages of absolute number of traffic accidents, two-hour time intervals during a day

146 VIII Meђународна конференција БЕЗБЕДНОСТ САОБРАЋАЈА У ЛОКАЛНОЈ ЗАЈЕДНИЦИ Ваљево, Хотел Дивчибаре, 18 – 20. април 2013

3.3. Spatial analysis of traffic accidents

The spatial analysis of traffic accidents includes an overview of places on road network with the highest frequency of traffic accidents and bus transit lines on which traffic accidents occur more frequently. Spatial analysis was conducted on the time period from 2007 to 2011, and the places of interest were roads, intersections and terminals. The street with the highest absolute number of traffic accidents for the observed time period was Ilica (an average number of 19 accidents per year), followed by Selska street (10 accidents per year). Traffic accidents on Ilica and Selska street are dispersed over those roads’ entire length, so none of their places with recorded accidents didn’t record more than 3 accidents per year. Years of traffic accident monitoring showed that Ilica and Selska street are the most dangerous roads due to high frequency of bus and other traffic flows. On Ilica the probability of traffic accident occurance is aided by insufficient share of yellow lanes, and on Selska street those lanes don’t even exist, so the effect is even greater. The probability of traffic accident occurance is also aided by inadequate traffic lane width, especially on northern part of Selska road. Table 3. Bus transit lines with the maximum relative number of traffic accidents Transit Average relative number of traffic line Transit line name accidents in the period from 2007 to number 2011 128 Črnomerec - Lukšići 5,17 109 Črnomerec - Dugave 2,28 118 Trg Mažuranića - Voltino 1,64 215 Kvaternikov trg - Trnava 1,41 121 Črnomerec - Karažnik 1,39 203 Svetice - Vinec - Krematorij 1,32 127 Črnomerec - Mikulići 1,29 227 Svetice - Gornji Bukovac 1,23 234 Glavni kolodvor - Kajzerica - Lanište 1,07 The with the highest number of traffic accidents is a large roundabout intersection of Dubrovnik Avenue and Jadranska Avenue („Rotor Remetinec“), in which about 6 accident happen every year. Besides the fact that a very large number of transit lines crosses this intersection (mostly from Savski most terminal), the number of traffic accidents is a result of poor safety characteristics of the intersection, which include three traffic lanes in the roundabout circle, access roads that have longitudinal inclination and poor visibility due to access roads that aren’t perpendicular to roundabout circle, also allowing higher speeds. The terminal that mostly lacks safety is „Črnomerec“, with an average number of 7 accidents per year. This kind of situation is caused by a large number of bus transit lines served by the terminal, presence of bus transit lines other than ZET, presence of illegally parked vehicles and movements of personal cars through terminal areas. If the number of traffic accidents on particular lines for a period from 2007 to 2011 were considered, results show spatial characteristics of each transit line. Bus transit line 220 („Črnomerec – Dugave“) has the highest absolute number of traffic accidents per year due to large bus frequency and lack of safety (already mentioned northern part of Selska street). Highest relative number of traffic accidents (Tab. 3) is on transit line 128 („Črnomerec – Lukšići“), which is a typical line with high longitudinal inclinations with insufficient lane widths, reduced visibility along road curvatures and the presence of improperly parked vehicles.

4. DISCUSSION

Besides the data about the number of traffic accidents, the database of ZET includes data about the number of persons involved in accidents (in absolute and relative manner), number of accidents according to driver’s experience, driver’s age and moment in driver’s shift. The database can’t provide, for example, data about influence of alcohol, influence of bad weather, speed restrictions along the network, usage of seat belts (in cars), usage of any other safety equipment or the age of buses. Therefore the database is almost entirely completed in terms of data about direct factors and very poor in terms of data about indirect factors. Because of that, it’s impossible to establish relations between direct and indirect factors. Continuous monitoring of other traffic as a part of the bus transit network in the City of Zagreb doesn’t exist so traffic volume can’t be eliminated for purpose of determining relations between other safety factors and traffic accidents which is a major drawback in the field of traffic safety.

147 Davor Brčić, Marko Slavulj, Dino Šojat, Daniela Bolčević Turčić TRAFFIC SAFETY INDICATORS FOR URBAN PUBLIC TRANSPORT

5. CONCLUSIONS

The analysis of absolute nuber of traffic accidents during the period from 2001 to 2011 found that the absolute and relative number of traffic accidents largely depends on the level of motorization in the City of Zagreb, which had its maximum during 2007 and 2008. As the level of motorization decreased, relative number of traffic accidents also decreased back to values which it had in 2001. Relative number of accidents during a week is proportional to traffic volume during each day, resulting in higher percentage of traffic accidents during work days with maxima at Mondays and Fridays, and minima during weekends. Relative number of traffic accidents during a day is a direct consequence of fluctuations of traffic flows, which reach its maximum value in the afternoon peak hour because probability of a traffic accident occurence depends more on duration but less on traffic flow intensity. During the afternoon peak hour an element that significantlly influences the level of safety is driver’s fatigue. Percentage of bus network’s yellow lanes in the City of Zagreb is less than 1%, but even the worse fact is that their percentage is negligible on roads with intense bus flows (Ilica, Selska street). If percentage of yellow lanes along city’s road network was increased, number of incidents would be reduced, resulting in decreases in number of traffic accidents. Reduction of number of vehicles operating at a transit line in the context of traffic accident reduction is a wrong approach because it conflicts transport demand. The reduction can only be achieved by corrections in the field of traffic engineering or civil engineering on bus transit network performed only after analysis of places with high probability of an accident occurance. For the purpose of analyzing a traffic accident database based on the correct data from GIS (GIS – geographical information system) is required. Such analysis coud be very productive on bus transit lines with high longitudinal inclinations. The traffic accident database given from ZET includes general information only and it doesn’t include more specific data about causes of traffic accdents, spatial characteristics of transit line routes or traffic flows on bus transit network. Detailed study of traffic accident causes with a proposed database would be sound basis for detection of traffic accident causality and determination of more precise measures to increase safety of bus traffic in the City of Zagreb.

6. REFERENCES

[1] Cerovac, V. (2001). Tehnika i sigurnost prometa, Fakultet prometnih znanosti Sveučilišta u Zagrebu, 23. – 25. [2] Directive 2008/96/EC of the European Parlament and of the Council of 19 November 2008 on road infrastructure safety management, http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:319:0059:0067:EN:P DF (01.03.2013.) [3] European Commission DG-TREN,Technical Assistance in support of the Preparation of the European Road Safety Action Programme 2011-2020, Final Report, February 2010 [4] Guide of “best practices” for the collection, management and analysis of the road accident data in urban zones, INTRAS, Valencia, Spain, 09/2007. [5] Podaci o autobusnom prometu ZET-a, http://www.zet.hr/autobus.aspx (24.01.2013.) [6] State of the art Report on Road Safety Performance Indicators, SWOV, 05/2005, SafetyNet [7] Statistički ljetopis Grada Zagreba 2011. http://www.zagreb.hr/default.aspx?id=1044 (24.01.2013.)

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