Traffic Safety Indicators for Urban Public Transport Čimbenici Sigurnosti U Javnom Gradskom Prijevozu
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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 – Zagreb 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, street 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, Croatia, [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, streets 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