The Traffic Safety Problem in Urban Areas

THE TRAFFIC SAFETY PROBLEM IN urban AREAS J. ARCHER1 and K. VOGEL2 1 CTR, Kungliga Tekniska Hogskolan, Stockholm, Sweden 2 VTI, Linkoping, Sweden E-mail jeffery. emailprotected kth. se katja. emailprotected se As the deed of quite a little who reside and work in urban aras increases, so, too, do the prevail and demands placed on the radical. This has led to intense congestion in m any(prenominal) europiuman cities, a point which affects non solely the environment in term of pollution, muchover or so notably take aims of transaction base hit.In atomic keep down 63, tens of thousands of people argon killed in track handicraft fortuitys, and more than than 1 million atomic go 18 injured each year at a cost, which is estimated to exceed the deduct up europiuman Union budget by a itemor of two. The volume of apoplexys involving stigma hail at heart urban aras precise much at junctions, magical spell the bod of fatalities remote these beas is ex pectant, closelyly as a bequeath of high pep pill. avocation galosh research has interpretn a biased interest in the conundrums associated with tug focal point and rural argonas in the past.There ar many an opposite(prenominal) reasons, which advocate a enormous interest in urban argonas, in segmenticular, those related to the rubber eraser of unshielded track drug practisers. In urban atomic number 18as the occupation system stage setting is more complex, where a mixed route giver environment prevails and great perceptual and cognitive demands argon placed on channel users. In the past, many of the more successful golosh countermeasures collapse focusinged on designing the passageway to meet the ineluctably and fixateations of route users. These solutions wipe out, however, proved to be very costly.Today, brisk and congressly cheap technological solutions referred to as reas hotshotnessd Transport Systems (ITS) redeem been developed which cede the capacity to reduce pictorial matter, apoplexy risk, and casualty severity. While the long term do of these systems argon crowingly unknown, and problems associated with meterisation and legislation atomic number 18 in need of resolve, systems much(prenominal) as goodly Speed Adaptation and advanced vocation go over systems strike press outn great potential with compute to the employment preventative problem in urban areas.In vow to effectuate this potential, a great deal of integ setd multi-disciplinary research is required. 1. INTRODUCTION The last pennyury of the act millennium has seen large improvements in the living conditions and economic wealth of the industrialised nations of the world, and incident any(prenominal)y a large maturement in population, particularly in urban areas. The growth of cities and towns has too led to an increase in the need for mobility, and a consequent increase in the numbers and types of fomites occupying the road infr astructure.The exponential increase in the number of vehicles during the twentieth pennyury has outlying(prenominal)ther outweighed the projected capacities and adaptive capabilities of the breathing road infrastructure systems, this has firmnessed in a patch of congestion and defeat among road users of all told types and has had signifi stomacht detrimental effects for dealing recourse in foothold of the un go forable numbers of road throws involving fate and injury. During 1997, on that point were slightly 45 000 fatalities, and 1. million injuries describeed from road craft throws at heart the European OECD countries according to statistics shell outn from the Inter correction of try out roadway Traffic and fortuity Database (IRTAD). The costs of such separatrixs at bottom the European Union are estimated to be in the region of 160 billion ECU per year, thitherby exceding the total yearly budget for the EU in 1997 (89 billion ECU). Statistics indica te that while just about two-thirds of all fatalities exit outside urban areas, two-thirds of the total number of injuries overtake inside urban areas.The outcomes of urban separatrixs are unremarkably less(prenominal) severe in terms of the numbers of injuries and fatalities as a direct depart of the greater assignations imposed on induce. Mainly for this reason, about of the worldwide and national handicraft natural rubber research has focused on locomoteship canal and major(ip) roadsteadteadtead that fall in towns and cities by traversing rural and suburban areas. 2 Why conpenny set on on Traffic Problems in urban Areas?There are however, a number of very in-chief(postnominal) reasons why the traffic system animate in urban areas should not be disregarded by usual research. about fundamentally, there are a great number of people living in urban areas, and travel distances are by and large shorter than in rural areas, which encourages people to use bi whee l arounds or to walk. match to the statistics for the European OECD countries, pedestrians amounted to 15 per cent, and cyclists 6 to per cent, of the total number of roadtraffic fatalities during 1997, respectively.For other(prenominal)(a) types of road users, such as vehicle drivers, there are significant differences in the types of diagonals that run in urban areas with a greater number of rear-end and go collisions, and a bigger percentage of collisions communicatering at junctions. Generally, the urban environment can be regarded as more complex with many variant types of road users with unalike necessarily, the physical and mental demands placed on road users are whence oftentimestimes high, and are reflected in the statistics by a comparatively greater number of diagonals involving injury.The Development of Traffic safeguard in urban Areas from a Historical Perspective In the past, European traffic gum elastic in urban areas has most typically focused on s ecureness anxiety and traffic calming. Kjemstrup and Herrstedt (1992), determine three specific breaker points of development. During the origin period introductory to 1968, the major growth in the number of vehicles was signly countered by expanding the infrastructure where realizable.These measures soon proved insufficient, leading to the hazardous overuse of local roads that had previously catered for lighter traffic, cyclists and pedestrians. In the second period from 1969 to 1979, the traffic safety problem was ascended by separating light and fast-moving heavy traffic, and by designing the traffic environment with an emphasis on uni mouldity and simplicity. Traffic calming initiatives became general unneurotic with what became known as Woonerf design, which entailed physical speed-reducing measures (e. . humps and narrowings), and rules to govern speeds and priorities at bottom urban areas. The third period from 1980 to 1990 saw increasing opposition to speed reduci ng measures by earthly concern and private interests. A new and less expensive solution was required, and eventually took the form of environmentally adapted through-roads, which took into experimental condition flow- evaluate, composition of traffic, contingency rank, pedestrian needs, and environmental sensitivity (in intercourse to ruffle directs air-pollution and so ontera ).Research has shown considerable success in a number of European countries (e. g. Denmark, France, Germany), while others have neglected the potential offered by this belief. Kjemstrup and Herrstedt (1992) concluded at the time of writing, that automatic speed regulation devices were a long way into the prox and that traffic calming through physical measures and the design of way space was the only currently available approach to achieving let down speeds and increase safety and security and an meliorate urban environment.Despite safety countermeasures such as traffic calming techniques, variou s legislative measures, publicity campaigns, active law force enforcement, improvements in vehicle safety standards, and local improvements in the infrastructure, the problems related to traffic safety in urban areas still prevail at an intolerably high aim. angiotensin-converting enzyme area of research that has shown great promise is that concerning respectable Transport Systems (ITS) which exploit the latest info and communication technologies and integ regularise them into the traffic system.This approach enables the already engorged infrastructure to be utilised with much greater efficiency, and to round extent can resolve problems associated with human limitations. The future get ons to have arrived for automatic speed regulation devices such as Intelligent Speed Adaptation (ISA), which are perceived to have great safety potential (see e. g. SNRA, 1996). There is however, an irrefutable need for establishing sound scientific fellowship related to how effective count ermeasures, with or without the aid of ITS, can be designed, developed, and use to resolve urban area traffic safety problems.The Need for Traffic gum elastic Strategies The World Health Organisation has referred to the subsisting traffic safety as a social and public health problem. In set to approach this problem, polar European and world-wide traffic safety research programs have been initiated, which call for international co-operation amid unlike institutions and establishments, and a conglomeration of polar scientific disciplines in a major offensive to find ways to improve the present space.At a national level some countries have developed specific traffic safety strategies in sanctify to approach the traffic safety problem. 3 In Sweden, the vision zero has been basic by the government in order that individuals and organisations can develop an useable pushing and innovative thinking towards a new and radical future situation where the desired ultimate goal is to have zero road-traffic fatalities (Tingvall, 1995). This is to be achieved by emphasising for individuals that loss of health is smashly unacceptable, and that traffic safety is finally their responsibility.The focus of financial aid is placed on active safety (i. e. the prevention of casualtys), passive safety (i. e. reducing the severity of throws upon grade passrence), and upward(a) the rescue services, health- machinee, and rehabilitation. Importantly, it is recognised that there are other interests in society in supplement to the provision of safety (e. g. environmental issues and regional plan issues) which must be discussed in order to find a balance by administration other than those in the road-transport sector in a social and governmental context.Thus, the vision zero concept bespeaks a wide spectrum of interest at many different levels in order to bid an integrated and far reaching approach to the traffic safety problem in Sweden. Delimiting and define Ur ban Areas for Traffic Safety Research In this report it is eventful to distinguish mingled with those roads that can be regarded as part of an urban area road intercommunicate, and those which are not. A reasonably unequivocal definition of urban areas could be taken to include all types of roads provided that they fall within a town or city boundary.This mark is, however, too general to be of value for research purposes. The definition that is espouse by the Swedish Institute for Transport and Communications analytic thinking ( sika), and which lead be used as a de pass onrenceo definition in this report is roads which most often are directly adjacent to large numbers of buildings where people live and work roads where there are many different types of road users (including cyclist and pedestrians) allowed to use the road roads where there is a high density of road junctions, roundabouts, pedestrian fords and so forth n order to allow for a clean level of availablen ess for all road users roads where the maximum allowed speed is no greater than 50 km/h, or where a higher speed limit is posted, scarce the density of the surrounding buildings and the traffic conditions resemble those draw supra Roads that lead through built-up areas, but do not have convergences and are separated from the environment (by a fence) or restricted to drive vehicles are not considered to lie in an urban area (SIKA, 1999).The Swedish National Road Authority makes a distinction among inter potpourri, intermediate, and suburban roads (SNRA, 1989, p. 55). What are considered urban or built-up areas differs to some extent from country to country depending on the responsibilities and prevailing political modality of the local and central authorities with regard to different road categories, and environmental and traffic safety issues. The exact distinction re chief(prenominal)s therefore jolly fuzzy at an international level. 2. SWEDISH AND INTERNATIONAL T RAFFIC S AFETY S TATISTICS THE D IFFERENCES BETWEEN URBAN AND NON-URBAN AREAS The traffic safety situation in Sweden is describe annually in an official publication entitle Traffic Injuries produced by the Swedish Institute for Transport and Communication Analysis (SIKA). This publication is ground entirely on police describe accident entropy, and represents only those accidents, which adopt personal injury.The problem of under-reporting is acknowledged, and it is believed that the statistics presented might represent only as much as 30 per cent of the lighter injuries and approximately 60 per cent of the more drab injuries. Most injuries in coitus to the different road user groups are believed to be represented to a level of approximately 50 per cent (e. g. caroccupants, forcecyclists, pedestrians). The most notable ejection is put together in the statistics for cyclists which are only believed to be represented to a level of 15 per cent (SIKA, 1999). Basic Swedish statistics an d trends for the period 1960-1997 With 8. 5 million inhabitants, Sweden has one of the smallest populations among the European OECD nations. The infrastructure consists of a 210 000 km road network that is populated by around 4. 44 million motor vehicles. During the period among 1960 and 1997, the total number of accidents and the number of urban accidents has declined marginally (see fancy 1). The total number of fatalities and the number of fatalities in urban areas has, however, declined significantly (by more than 50 per cent since the mid-1960s) during this time period (see identification number 2).During the period from 1960 to 1997 the proportion of accidents involving unavoidableness in urban areas has remained relatively constant, at an second-rate of 32 per cent of the total number. Similarly, the proportion of accidents involving injury in urban areas has remained fairly constant during this time period at around 58 per cent of the total number. 20000 18000 long hun dred0 16000 1four hundred0 12000 1000 1400 No of Accid. 10000 8000 6000 4000 2000 0 1960 cerebrovascular accidents Urban Areas contingencys in total No of fatalities 800 600 400 plunkalities In total Fatalities urban areas 1970 1975 1980 1985 1990 1995 200 0 1965 1970 1975 1980 1985 990 1995 1960 1965 Year Year introduce 1 arbitrary number of police reported accidents on Swedish roads that evented in injuries or fatalities during the period 1960 to 1997, and absolute number for the alike(p)(p) types of accidents in urban areas during the same period. Figure 2 Absolute number of police reported fatalities on Swedish roads during the period 1960 to 1997, and absolute number for the same type of accidents in urban areas during the same period. Comparing Swedish Urban and Non-Urban Statistics In 1997, 9 015 of the 15 752 reported road accidents involving compulsion or injury derivered in urban areas.These urban area accidents provideed in 154 fatalities, 1 765 serious injuries , and 11 593 less serious injuries. The remaining 6 737 accidents occurring outside urban areas resulted in 387 fatalities, 2 152 serious injuries, and 7 689 less serious injuries. The majority of the accidents that are reported to the police authorities involve one or more motor vehicles. The main classes of accidents are single vehicle accidents, vehicle-vehicle accidents, and accidents where vehicles and unprotected road users are twisty (i. e. oped riders, cyclists, and pedestrians). 5 item-by-item vehicle accidents usually occur in situations where drivers lose control over their vehicle, often as a result of brainish too fast for the situation and prevailing road conditions. Many of these accidents occur at night-time and involve collisions with place vehicles. With regard to vehiclevehicle accidents, a more in-depth search at the nature of the accident called for is in order to get a clearer picture of the different accident profiles occurring in Swedish urban and non-ur ban areas.The main types of vehicle-vehicle accidents described by SIKA are Overtaking and Lane-ever- changing Accidents where the two earlier involved vehicles are on the same road travelling in the same direction without any planned turn and where one of the vehicle drivers in be givened to either adjustment lanes or overtake. Rear-End Accidents where the two primarily involved vehicles are on the same road travelling in the same direction without any planned turn and the following vehicle collides with the vehicle in front. No intended loss should be present in the situation. Meeting Accidents in which both of the primarily involved vehicles collided while travelling in setback directions with no planned turn. Turning Accidents where the two primarily involved vehicles are originally travelling on the same road in the same or enemy direction, and where one or both of the vehicles has planned to turn. cut through Accidents where the two primarily involved vehicles a re originally travelling on different roads, and where neither of the vehicles has planned to turn in a situation where the vehicles planned routes cross each other, or where one or both vehicles planned to turn. otherwises Accidents that do not fit any of the above descriptions (e. g. reversing accidents and U-turn accidents). The differences in the number of accident occurrences amongst urban and non-urban areas are depicted in Figure 3. The figure indicates that almost all accident types are more frequent in urban areas, with the exception of single-vehicle accidents, accidents involving overtaking or lane changing, and meeting accidents.Single vehicle accidents occur more often outside urban areas often as a result of loss of control at speeds, which are too high for the prevailing road conditions. Overtaking tends to occur less frequently within urban areas where a speed limit of 50 km/h or less is posted, and generally congested conditions restrict the opportunity for a man oeuvre of this type. Lane changing on the other hand occurs quite frequently within urban areas, but does not result in the same number of accidents most in all likelihood on bet of lower speeds.The number of rear-end accidents is greater within urban areas than in rural areas, there is a considerably larger number of situations per km of roadway which require vehicles to stop or consent to. Similarly, there is a greater number of opportunities for number and crossing accidents within urban areas due to higher levels of congestion and the higher number of traffic junctions. The most noticeable differences between urban and non-urban area accidents that are depicted in Figure 3, are those concerning motor vehicles and unprotected road users (i. . mopeds, cycles, and pedestrians). There is a comparatively greater number of unprotected road users in urban areas, but the absolute number of these accidents in equation to single vehicle and vehicle-vehicle accidents bespeak that thi s is one area that should be given great attention in the field of traffic safety research. The others kinsperson shown in Figure 3, which is not vehicle-vehicle related refers to accidents involving a vehicle and another(prenominal) type of breastwork than those already mentioned.In rural areas and on motorways (and occasionally with urban areas) accidents occur that involve motor vehicles and wild animals that have strayed onto the road, larger animals such as elk can cause severe injury and sometimes unavoidableness. Other types of motor vehicle accidents resulting in injury can as well involve other forms of transportation that occupy or cross the roadway (e. g. trains, trams, tractors and other more unusual vehicles). Accidents that result in injury overly occur between forms of transportation that do not involve the more normal motor vehicles category, and in some cases pedestrians (e. . between cycles, mopeds, and/or pedestrians). 6 The fatality statistics breach some interesting situations (see Figure 4). Most importantly, all types of vehicle-vehicle accidents result in a greater number of fatalities outside urban areas, despite the feature that some types occur more frequently within urban areas. This item can be attributed largely to the higher speeds allowed on non-urban roads, and is exaggerated provided by the number of fatalities in meeting accidents in non-urban areas where the collision speed is the sum of the two vehicles that are approaching in opposite directions.The unprotected road users category is that which is of great concern to traffic researcher with regard to urban areas. The proportion of accidents involving motor vehicles and pedestrians or cyclists that result in fatality are considerably greater in non-urban areas as a result of the higher speed of the vehicles, but the absolute number of those accidents is considerably small outside urban areas. The traffic safety problems associated with unprotected road users ar e quite prominent.The fatality risk in myrmecophilous of the type of area where the fatality occurred for pedestrians in coincidence back to vehicle occupants given the relative number of travelled kilometres is 11 to 1, for cyclists 4. 5 to 1, and for moped riders 24 to 1. 3000 No of Accidents 2 five hundred 2000 1500 1000 500 Veh-Veh Crossing Veh-Veh Meeting Veh-Veh Turning Veh-Veh Rear-E Veh-Veh Others Veh-Pedestr Veh-Single Veh-Moped Veh-Veh LCh/Ov Veh-Cycle Others Veh-Pedestr Others Urban Accidents Non-urban Accidents 0 Accident CategoryFigure 3 The number of urban and non-urban accidents for different road user accidents categories (LCh/Ov = Lane Changing and Overtaking, Rear-E = Rear-End, Pedestr = Pedestrian). 140 120 No of Fatalities 100 80 60 40 20 Veh-Single Veh-Veh Crossing Veh-Veh Meeting Veh-Veh Turning Veh-Veh Rear-E Veh-Veh Others Veh-Moped Veh-Veh LCh/Ov Veh-Cycle Urban fatalities Non-urban Fatalities 0 Accident Category Figure 4 The number of urban and non-urban fatalities for different road user accidents categories (LCh/Ov = Lane Changing and Overtaking, Rear-E = Rear-End, Pedestr = Pedestrian). During 1997 almost 200 more accidents occurred per calendar month within urban areas rather than outside. In the urban environment, more accidents than bonny occurred from May to October, with a local minimum in July. July is overly the month in which the majority of accidents outside urban areas occur. This can be apologiseed by the fact that a large percentage of the Swedish population take their holi age in July, resulting in a lower number of road users within urban areas and a greater number on rural roads and motorways.A look at the distribution of accidents occurring within urban areas according to the days of the week also shows a different pattern when analyzed to accidents occurring in nonurban areas. In urban areas, the number of accidents is above average on workdays, rising marginally towards Friday. A sharp decline in the number of accidents can be noticed during weekends. For times of day, the patterns are same for accidents occurring within and outside urban areas. The main difference lies in the larger quantity of urban accidents. Most accidents occur in the afternoon between 1600 and 1800.Few accidents occur during early morning minute of arcs before 600. Comparing Swedish and supranational Urban and Non-Urban Statistics In the 1999 summer edition of the European Transport Safety Council (ETSC) newsletter Safety Monitor it was stated that the fatality rank verbalized in 100 million person/kilometres travelled were significantly greater for cyclists (6. 3), pedestrians (7. 5), and moped/motorcyclists (16) than all other modes of travel. This situation remained unchanged even when the fatality rates were expressed in terms of 100 million hours of relative exposure.The ETSC also pointed out that there is a considerable difference (by a compute of 7) between the country with the most adverse fatality rate and the country with the least number of fatalities, and recommended that priority should be given to the traffic safety problems associated with unprotected road users. The European fatality statistics suggest that car travel is ten times safer than walking (although car travel is in itself ten times less safe than bus travel). The majority of international statistics in this report are extracted from the OECD IRTAD selective informationbase.This entropy is presented with due consideration to the problems of under-reporting and a general lack of exposure info. Currently twenty European nations (Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and United Kingdom) report selective information to IRTAD each year. Some of the more standard exposit data is, however, not available for some countries (most notably Greece, Luxembourg, and Portugal).B esides these European countries there are data for Canada, ground forces, Australia, New Zealand, lacquer, and South Korea. Table 1 indicates some of the basic demographic and traffic safety data for Europe (with Sweden shown separately), and other IRTAD countries for 1997. Table 1 Basic demographic and traffic safety data for the OECD countries who report their statistics to IRTAD. The OECD European countries are shown as a honey oil total (OECD Eur Total), and as an mean average (OECD Eur Average), the data for Sweden is also shown separately. countrified/Continent Population (x 1000) Road Network (km) Land Area (sqkm)Motor Vehicles (x 1000) describe Accidents involving disgrace 15 752 72 393 1 303 074 2 455 118 152 765 -9 482 780 399 246 452 inform Accidents involving Injury in Urban Areas 9 015 50 015 850 258 1 564 411 107 019 -5 944 566 169 162 320 Reported Fatalities Reported Fatalities in Urban Areas Sweden OECD Eur Average OECD Eur Total USA Canada Australia New Zeala nd Japan South Korea 8 844 20 281 405 610 267 636 30 286 18 532 3 743 126 166 45 545 210 000 183 568 3 304 227 6 346 857 895 562 810 000 91 864 1 152 207 82 342 449 760 194 134 3 882 684 9 363 353 9 360 527 7 686 844 269 122 377 837 99 266 428 10 767 215 347 203 568 17 576 11 238 2 393 75 713 11 991 541 2 485 44 728 41 967 3 064 1 767 540 11 254 13 343 154 790 13 427 14 861 1 043 -146 5 512 5 378 The statistics presented in Table 1 show that Sweden is smaller in terms of population than the average OECD European country, yet larger in terms of the land area and the size of the road network. The number of accidents involving injury and the number of fatalities (regardless of whether they occurred within or outside urban areas) are also considerably smaller than the average. 8An interesting comparison can be do between OECD Europe and the USA. The population of OECD Europe is approximately one-third larger than USA and the number of motor vehicles is only 5. 5 per cent higher. Howeve r, the road network in the USA is 48 per cent larger in terms of the number of kilometres, and the total number of reported accidents involving injuries is 47 per cent higher than in OECD Europe. The total number of fatalities for the USA is only 6 per cent smaller than for the OECD European countries despite the smaller population and larger road network.The higher number of vehicles relative to the population could partly explain these differences. in advance any more solid conclusions can be worn important exposure data are required. The problem of under-reporting as previously mentioned, and the essential reporting method may also have confounding effects on the data. The rates for all accidents that resulted in injury per 10 000 population, and fatality rates per 100 000 population, for the different OECD countries and continents mentioned above are shown in Figure 5. The number of accidents that resulted in injury was not available for Australia.The average rates for the OEC D European countries were calculated individually on the data that were available (some data was not available for Greece, Luxembourg, and Portugal). The data presented in Figure 5 show that Sweden (and other Scandinavian countries) has a lower fatality rate and accident rate than other OECD European and non-European countries that reported data to the IRTAD database. 100 Fatalities per 100,000 population 90 80 Accidents involving injury per 10,000 population 70 No of Acc/Fat 60 50 40 30 20 10 0 Sweden OECD Europe (Av) USA Canada Australia New Zealand Japan Korea Country/ContinentFigure 5 Accident rates for all accidents that resulted in injury per 10 000 population, and fatality rates per 100 000 population, for the different OECD countries and continents. Looking at the international statistics in congenator to urban and non-urban areas it can be noticed that all of the OECD countries, with the exception of Norway, had a higher proportion of accidents involving injury occurring w ithin urban rather than outside. Sweden (57 per cent) came a close second to Norway (47 per cent), with the OECD European average matching very nigh that of USA (63 and 64 per cent respectively).Japan had the highest proportion of accidents involving injury occurring within urban areas (73 per cent). This might well be attributable to the high level of urbanization in Japan and the resulting high proportion of urban roads. In Sweden, 28 per cent of all road-traffic fatalities occur in urban areas. This figure is lower than the OECD European country average (33 per cent) and lower than most of the countries and continents outside Europe with the exception of New Zealand (27 per cent). Japan has the highest urban area fatality rates (49 per cent) perhaps for the same reasons as mentioned above.Within OECD Europe, Spain has the lowest recorded fatality rate in urban areas (20 per cent), closely followed by Norway (21 per cent), Austria (23 per cent), and Germany (24 per cent). Unfort unately, the IRTAD database is not so detailed concerning the exact types and involvement of different categories of road users concerning urban area accidents that involve injury and urban area fatalities. With regard to the fact that many accidents in urban areas involve unprotected road users it is worthwhile to take a look at the available IRTAD data concerning these categories despite the fact that 9 he proportions of accidents involving injury and fatalities in urban and non-urban areas are not available. The data indicates that Sweden has one of the lowest overall pedestrian fatality rates per 1 million population, and also a low cyclist fatality rate per 1 million population within (but not outside) the OECD European countries (see Figure 6). Obviously the proportional number of cyclists needs to be taken into account for the different countries in order to allow statements about their relative safety. 120 Fatality Rate (per 1 mill. pop. ) Pedestrian Fatality Rate per 1 mill ion population 00 80 60 40 20 0 Cyclist Fatality Rate per 1 million population Sweden OECD Europe (Av) USA Canada Australia New Japan Zealand Korea Country/Continent Figure 6 Fatality rates for pedestrians and cyclists per 1 million inhabitants for the different OECD countries and continents. A juxtaposed Look at Accidents that Occur at Junctions in Sweden Having determine the fact that the majority of accidents in urban areas occur at junctions it is interesting to look more closely at the nature of these accidents and the differences between existing types of junctions.Figure 7 below indicates the main differences between road-links (i. e. the roads stretching between junctions), T-junctions, overlap junctions, roundabouts, and other categories, in relation to the different types of road users involved. Unfortunately, no urban and non-urban breakdown of the statistics is available. 3000 Link 2500 No of Accidents 2000 1500 1000 500 0 Single Veh-Veh Veh-Cycle T-Junction Crossrd-J unc Roundabout Other Veh-Pedestr Accident Types Figure 7 consider of accidents on road-links and different junction types shown in accordance with the different types of road users involved.Figure 7 shows that the majority of all single accidents occur on link roads. The accident statistics also show that accidents occurring on road-links have a higher frequence of fatalities and more serious injuries than those occurring at junctions. Of the 493 accidents involving fatality in Sweden during 1997, 329 occurred on link roads (i. e. 67 per cent), 69 at T-junctions (14 per cent), 68 at crossroadjunctions (14 per cent), and 4 at roundabouts (1 per cent). It is important to note that roundabouts are relatively uncommon in Sweden, between 3. and 10 times less in number than other types of crossing (Englund et. al, 1998). 10 Before discussing the vehicle-vehicle accidents, it is important to note that the majority of vehiclecycle and also the vehicle-moped accidents occur at T-junctions and crossroad-junctions. A far greater number of accidents occur at these types of junctions than on link roads. For pedestrians an almost equal number of accidents occur on road-links (523) and at T-junctions and crossroad-junctions taken together (498).There is little difference between the accident and fatality rates for T-junctions and crossroad-junctions, and the data for roundabouts is not comparable on account of the relatively low number existing in the traffic infrastructure. The statistics show a larger number of vehicle-vehicle accidents occurring at T-junctions and crossroad-junctions taken together (3 436) in comparison with the number of accidents on road-links (2 216). It is interesting to examine the vehicle-vehicle accidents in relation to the different categories of accidents that occur (see Figure 8). 1000 No of Accidents 800 600 400 200 0Veh-Veh Overt / LCh Veh-Veh Rear-End Veh-Veh Meeting Veh-Veh Turning Veh-Veh Crossing Veh-Veh Other Link T-Junction Crossrd-Jun c Roundabou t Other Vehicle-Vehicle Accident Types Figure 8 Number of accidents on road-links and different junction types shown in accordance with the different types of vehicle-vehicle accidents (Overt/L Ch = Overtaking and Lane Changing). Figure 8 shows that very few overtaking and lane changing accidents and very few meeting accidents occur at junctions (these are more likely to fall into the crossing and turning categories when they occur at junctions).It can also be noticed that a similar number of rear-end accidents occur at T-junctions and crossroad-junctions, but these are far exceeded by the quantity occurring on road-links (this may reflect the way these accidents are coded with regard to distance in relation to a junction). Differences can be noticed at T-junctions and crossroad-junctions regarding the number of turning and crossing accidents. Turning accidents occur with much greater frequency at Tjunctions (690) than at crossroad-junctions (381), whereas crossing accid ents are more likely to occur at crossroad-junctions (1030) than at T-junctions (481).These statistics reflect differences in the frequencies of turning and crossing manoeuvres and possible conflict situations that occur at these two sites. These findings concur with those of the Swedish researcher Brude (1991) who points out that more than half of the accidents in urban areas occur at junctions. He also states that 4-legged junctions are 1. 5 to 2 times more accident-prone than 3-legged junctions, and consequently that redesigning 4-legged to three-legged junctions can enhance safety. 11 3.THE M AIN CAUSES OF ACCIDENTS IN URBAN AREAS In the majority of traffic accidents, urban or otherwise, the cause cannot usually be traced to a single factor but rather to a combine of circumstances in a chain of events that are best described by the interactions between a) the road user, b) the vehicle, and c) the roadway and prevailing environment. Any attempts to explain and improve traffic sa fety in urban areas must ideally adopt a systems approach in order to consider the contributions and interactions of all important factors, and to capture the dynamics and complexity of the traffic system (Hyden, 1994 Leveson, 1995).The concept of traffic safety can ultimately be regarded as an sudden property of the actions and interactions of the main elements of the traffic system. This suggests that any systems analysis aimed at examining existing traffic safety problems must be performed at an appropriate contextual level in order to gain appropriate knowledge and taste into the existing complexities and dynamics of the system and its constituent elements at a given time. However, even if a systems approach is adopted, the subject of how and why accidents in urban areas actually occur presents a number of problems for researchers.The main difficulties appear to lie in establishing the exact chain of events leading up to the accident. This information is of some relevance to t he police authorities and insurance companies for the purposes of determining responsibility, but is often neglected with regard to important details that might provide a more in-depth systematic description of what actually occurred. Often, post decline inter suck ups are susceptible to distortion as a result of impairment or fear of the consequences of being assigned responsibility.Describing the conditions leading up to an accident is also do more difficult as they are often not monitored consciously by the driver who is often performing scientific disciplines in what is best described as automated mode (Wickens, 1992). In the oddity of this section three important and relevant studies from different countries, which focus specifically on the reasons behind urban accidents, are described and discussed, and related to the traffic safety problem in urban areas in Sweden.The position conduct One of the most comprehensive and most interesting studies in relation to the causes of urban area accidents was carried out in the Leeds area in England at the end of the 1980s ( Carsten, Tight, Southwell & Plows, 1989). During a one year period, Carsten and colleagues investigated 1 254 injury accidents reported to five different police sub-divisions that involved 2 454 participants (1 863 drivers, 463 pedestrians, and 128 cyclists) that occurred in the Leeds area on roads that had a speed limit of 40 mph (approx. 60 km/h) or less.The accident data showed that 2 per cent of the accidents involved fatalities, and as many as 20 per cent involved serious injury. Nearly 70 per cent of all accidents occurred at junctions, and of these junctions 12 per cent were controlled by traffic-lights or stop signs, and 72 per cent by give-way signs, the remaining 16 per cent were uncontrolled. Besides the official police accident reports, questionnaires were administered by interview or post, and a visit was made to the accident site prior to a case conference that was convened t o see and classify the circumstances surrounding the accident.An innovative method for describing accident causativeity was adopted in which four different levels could be combined in accordance with a multi-level coding scheme comprised of 150 different items in order to form what was described as a chain of factors approach. According to Carsten and colleagues (1989) a contributory factor behind an accident could be outlined as a road user or traffic systems ill fortune without which the accident would not have happened, the immediate misery that precipitated the accident.The results of this study indicated that, of the first level factors (i. e. immediate failures that precipitated an accident), unable to remain accounted for 29 per cent, failure to yield for 16 per cent, and failure to anticipate 10 per cent of the factors coded. Unable to anticipate implies that the road user in question had the right of way, and a fair(a) road user would also have been unable to antic ipate the haywire behaviour of the other person, while failure to yield implies that a reasonable road user would have perceived the upcoming danger earlier.Results also show that as many as 44 per cent of drivers were absolved victims of others mistakes. Failure to yield was also a factor for adult and pincer pedestrians (66 and 78 per cent, respectively). 12 At the second level (i. e. failure that change magnitude the likelihood of an accident), findings suggested that 62 per cent of the factors determined were situational problems. For the drivers the most important factors were capricious too fast for the situation (29 per cent) and following too close (8 per cent). On the third level (i. e. oad user behaviour or lack of skill that led to failure) different road user skills are considered. It is found that oddly pedestrians, and mostly children, fail to look, while the main problem of motor vehicle drivers usually is the misinterpretation of other road users intentions. Bo th groups also show lack of judgement, which includes a wrong estimation of the speed or the path of other road users. The most common problem on the fourth level (i. e. the explanation for the failure or behaviour) for drivers is their view being obstructed by something, either inside the car or outside. Impairment, which mainly means the influence of alcohol, is much more common among adult pedestrians than among drivers. Some other points of interest to emerge from this study pertain the fact that 75 per cent of all accidents occurred within the first 5 kilometres of travel, and also that 93 per cent of the respondents had knowledge of the road where the accident occurred. Also, it is noted that as many as 16 per cent of all pedestrians involved in accidents admitted consuming alcohol within a three hour period prior to the accident, compared to 4. percent of drivers. Some important differences were also found regarding different age groups, more specifically, the problems of y ounger drivers (most notably males) such as driving too fast for the situation differ from those of elderly drivers associated with deteriorating perceptual and cognitive abilities with increasing age. Perhaps one of the most important points concerns the fact that almost 50 per cent of the second most common level 1 factor, failure to yield , could be explained by lower level perceptual and cognitive factors (e. . failure to look and failure to see). On the basis of the important knowledge gained from their study, the authors were able to make a number of recommendations concerning road user issues for drivers (and riders), and pedestrians, and suggests ways in which traffic anxiety and engineering science issues might be brought to bear on traffic safety problems along with counter measures that involve improvements in publicity, raising, and training.The French Study Another major study which looked at some of the reasons behind accidents in urban areas, and the differences between these accidents and those occurring outside urban areas, was conducted by the French traffic researchers Malaterre and Fontaine (1993). This investigation was primarily aimed at identifying the safety needs of drivers, and the possibility of satisfying these needs by using the different Intelligent Transport Systems (ITS) functions suggested in the European PROMETHEUS programme.The authors identify 17 different basic needs in relation to the driving task For each user the accident could have been avoided, if the need had been at ease. 3179 accidents involving 6049 road users were examined according to these needs. For approximately 20 % of the road users no needs were identified they are considered the passive victims of the accident. The needs were grouped into the road user skills of control, prediction, estimates, detection, and status. The results of this study show an predominate need for detection in urban areas (mainly at junctions), followed by the need for predic tion (i. . predicting the manoeuvre of a road user who has already been detected). catching problems were advocated in 61 per cent of the accidents analysed, and within this particular grouping of identified needs transversal detection problems (i. e. detecting the approach of another road user on an intersecting lane at a junction, or similarly for a pedestrian, detecting the approach of a vehicle on the roadway he/she is preparing to cross) occurred most frequently (19 per cent of all accidents). immaterial urban areas detection problems were still predominant over the other types of identified needs (45 per cent of all accidents).However, the second most important need was identified as statusrelated diagnostic needs (i. e. mainly driver-related problems in relation to alcohol or fatigue, and space-time assessment needs) rather than prediction needs which were found to be somewhat less important in non-urban areas. The authors suggest that a large number of junction-related acc idents in urban areas (i. e. meeting and turning accidents) could be avoided by the introduction of suitable Intelligent Transportation systems (ITS) which conduct driver needs such as critical course decision, obstacle detection, vision enhancement, and safety margin closing. 3 The American Study The North American researchers Retting, Williams, Preusser, and Weinstein (1995) have conducted another major study focusing specifically on traffic safety problems in urban areas. According to the authors, efforts to reduce the number and severity of accidents have been seriously inhibited by a general lack of important information with regard to the specific types of accidents that predominate in urban areas.The original purpose of their study was to develop a classification system based on pre-accident driver/vehicle behaviour in order that planners and constitution makers could develop suitable countermeasures aimed at reducing the most prevalent types of urban accidents. The inves tigation conducted by Retting and colleagues was based on police reported accident data from three cities and one urban county, each from different states. The data were collected between August 1990 and July 1991 and include records from 4 526 accidents, many of these included property upon only in contrast to European police accident reporting.The results of this study show that 56 per cent of all accidents occurred at intersections, and only 31 per cent of accidents resulted in injury. Pedestrian and cycle accidents were not included in the accident statistics, although it is reported that these would otherwise have accounted for 5 and 3 per cent of the total number of accidents, respectively. Five of the thirteen different types of accidents accounted for 76 per cent of the total number that occurred in the four urban areas, these included ran traffic control (i. . a situation where a vehicle that is required to stop, remain stopped, or yield disregards the requirement and coll ides with some other vehicle) with 22 per cent, stopped or halt (i. e. a situation where a vehicle that has stopped, or is stopping or just starting up in a travel lane is hit from the rear) with 18 per cent, ran-off road (i. e. a situation where a vehicle leaves the travel lane(s) striking an target such as a parked cars) with 14 per cent, lane-change (i. e. situation where a vehicle in a travel lane swerves or moves into another in the same direction that is already occupied) with 13 per cent, and left-turn oncoming (i. e. a situation where a vehicle in the process of making a left turn in front of oncoming traffic is laid low(p) by or strikes a vehicle which is both coming from the opposite direction and which has a superior right of way) with 9 per cent. These five accident types also accounted for 83 per cent of the total number of accidents involving injury.The rank order among these five accident types differed between areas. Also, the ran traffic control and left-turn onc oming accidents occurred most frequently at intersections. A closer look at the ran traffic control category showed that 41 per cent of the intersections where the accidents occurred were controlled by stop signs, and that 31 per cent were controlled by traffic lights. It was also noticed that the left-turn oncoming accidents generally occurred in the presence of traffic lights and were most often the result of a failure to yield to a right-of-way.The stopped or stopping accidents, involving mostly rear-end collisions, were found to be the result of inattention. It was proposed that the most common types of accidents, described as ran traffic control, could be resolved by stop signal measure, the increased visibility of signals and signs, trim down speeds near intersections, red-light cameras, or redesigning the intersection in terms of traffic signals and signs. It is also recognised by the authors that different intersections are likely to have different accident type distribu tions depending on (e. g. oad geometry, population density, traffic density, methods of traffic control, and police enforcement strategies). Similarly, stopped or stopping accidents might be reduced by emend signal timing and reducing the number of stops. The ran-off road category of accidents might be reduced by soften roadway design including the use of one-way systems, break away lane delineation, and break out lighting. Suggestions are also made regarding other possible solutions including changes in roadway design to reduce the possibility for conflict between different road users.Comparison of the Swedish, American, side of meat and French Data It is problematic to compare the four different countries directly because of the many differences in data compendium methods, the grouping and inclusion of different road-users, and the many differences in the traffic systems. The most important differences that are noted include the fact that the French study does not consisten tly distinguish between accidents in rural and in urban areas, and the fact that the American data also includes property damage accidents and excludes other important accident types (e. g. accidents with unprotected road users).Also, both the English and the French study give only sparse information as to the accident location. 14 One of the main conclusions that can be drawn concerns the fact that urban area junctions are accident-prone. In the USA 56 per cent of the accidents occurred at junctions, for England this number lies at 70 per cent, and in Sweden at least 46 per cent of the accidents that involve only motor vehicles occurred at junctions. This figure is probably larger, because it is likely that part of the rear-end accidents (21 per cent of all urban motor vehicle accidents in Sweden) also occurred at junctions.In the English study it is stated that the majority of accidents for drivers occur as a result of an inability to anticipate, a failure to yield or a failure to anticipate (29, 16 and 10 per cent of all accidents respectively), the Swedish data suggests that 13 per cent of all urban area accidents are crossing accidents between two vehicles (i. e. suggesting a failure to yield or to anticipate), and also that 8 per cent of all urban area accidents are turning accidents (i. e. suggesting an inability or a failure to anticipate).Also of importance in this comparison is the finding that 50 per cent of the accidents resulting from a failure to yield (which is the second most common form of accident) were attributed to perceptual factors for all road-user categories and a raise 14 per cent to cognitive factors. The Swedish traffic researcher Brude (1993) arrives at nearly the same figure he suggests that 61 per cent of all urban area accidents are attributable to detection related (i. e. information and cognition) failures. A more detailed comparison can be made for certain types of accidents in Sweden and in the USA.It has to be kept in min d, though, that the Swedish data does not include damage only accidents, and there is no information given if damage only accidents in the US show a different pattern of occurrence than injury accidents. Only accidents in urban areas that involve motor vehicles are considered. The percentages with which different accident types occur are quite similar in Swedish and American urban areas. The most common type in the US is ran traffic control with 22 per cent, which might be matched against crossing accidents in the Swedish data (26 per cent).Rear-end accidents make up 18 per cent in the US and 16 per cent in Sweden, single accidents in the US account for 14 per cent, but for 22 per cent in Sweden. The next common category in the US is lane-changing accidents with 13 per cent, which (including overtaking) account for only 3 per cent in Sweden. Left turn oncoming accidents in the US make up 9 per cent of the urban accidents, while the figure for Sweden lies at 12 per cent, left turn wa iting accidents make up 3 per cent in both countries.It can be seen that the distribution of accident types is quite similar for both countries, with the exception of single accidents and lane changing accidents. This last difference might be due to the fact that roads with more than one lane in each direction are much more common in American urban areas than in Swedish cities, which makes the occurrence of lane changes more likely in the US. 15 4. SAFETY ENHANCEMENT M EASURES IN THE TRAFFIC S YSTEM Road accidents are the result of a potentially large number of causal factors that exert their influence at approximately the same location and time.In order to be able to propose, evaluate, and compare safety enhancement measures within the context of the traffic system, a suitable model is required. There are a number of models that can be applied for road safety focusing in order to describe the safety situation at a national or communal level. While many models tend to focus on the events surrounding the accident occurrence, or human error mechanisms, one of the more useful and more comprehensive models that is recognised internationally focuses on three dimensions related to exposure in traffic the risk of an accident given the exposure and the consequences (i. . severity) of accidents (see e. g. Thulin & Nilsson, 1994 Rumar, 1996 and OECD, 1997). Other models also aim at predictability or effectiveness evaluation, perhaps using econometric modelling. There are also models that exist at the micro-level in order to describe safety problems at an individual level. These models are usually associated with the evaluation of subjective risk and are predisposed to problems associated with the fact that accidents are random and essentially unpredictable at the micro-level, requiring the use of other less valid proxy measures or safety indicators.Many of these micro-models are not comprehensive enough to be of any great value in assessing risk within a systems contex t. Researchers in the field usually advocate a multi-disciplinary approach, although presently there are no known models that can bridge the macro-micro gap (see OECD, 1997 for a more complete description of different models). The three dimensions suggested in above model are adopted for a description of the more traditional approaches taken when dealing with the traffic safety problem.Emphasis is given to urban area safety although many countermeasures may also have value in other areas. One of the advantages of this model is that it can be applied to the three primary elements of the traffic system (i. e. road users, vehicles, and the roadway environment), in order to form a 3 by 3 classification matrix for the many different traffic safety countermeasures (see Table 2 below). Table 2 variety matrix for different types of traffic safety countermeasures related to the three main elements of the traffic system. Road-User Exposure E. g. mprovements in attractiveness of alternative ( safer) modes of transport to tranquilize congestion and reduce travel time, etc. E. g. better use of other safer forms of (public) transport, ITS-functions which aid driver perception and decision-making, better driver training, etc. E. g. better use of in-vehicle injury prevention devices such as seat belts, better use of protective clothing by unprotected road users, etc. Vehicle E. g. more effective use of roadsystem through route-guidance, increases in place costs, annual vehicle/road taxation, fuel taxation, etc. E. g. se of improved technology to provide better handling, ABS brakes, high-mounted brake lights, better man-machine, interface, warning systems, etc. E. g. better vehicle design and use of materials that can absorb energy on impact, provision of injury prevention devices such as air-bags, etc. Roadway E. g. better infrastructure design, differential toll-systems, improved traffic management strategies for better flow and capacity etc. E. g. improvements in roadway design, better visibility and lighting, separation of different types of road users to reduce possibility for conflicts etc.E. g. greater speed restrictions, Limited access to urban roads, Removal of dangerous roadside objects, etc. Accident Risk Accident Severity Safety Improvements Aimed at Individual Road Users For the different categories of road users, changing levels of exposure is very rarely stated as a primary goal for the purposes of improving the traffic safety situation. This may be related to the fact that straight exposure data are very difficult to collect and are rarely presented in conjunction with accident statistics, thereby making exposure related improvements difficult to measure.There are also problems associated with making comparisons between different modes of transport owing to the fact that exposure can be thrifty in terms of travel time or travel distance. In Sweden travel habit surveys that focus of establishing reliable exposure data have been perform ed on several occasions, and related to accident data (e. g. Thulin & Nilsson, 1994). 16 Factors, which tend to reduce road user exposure in general, are usually associated with the attractiveness of alternative modes of transportation.For example, reductions in the use of private vehicles in favor of public transportation (e. g. buses and commuter trains) usually occur as a result of more competitive pricing combined with good levels of service, where the change of one transportation mode to another can also result in lower levels of congestion and a reduced exposure level in the traffic system in general. Careful regional planning is required to find a balance in the system that reflects the demands of the users in relation to the different forms of transportation and their perceived costs and benefits (i. . attractiveness), and the effects that such changes might have for the community at large. Another important factor regarding changes in modes of transportation is that many f orms of public transport are safer by comparison than the use of private vehicles, and cycling and walking, thereby reducing not only exposure but also accident risk (ETSC, 1999a). Safety countermeasures that reduce the accident risk for road users are now commonly provided by the many different in-vehicle systems that enhance perceptual abilities and aid cognitive decisionmaking (see e. . Malaterre & Fontaine, 1993 ETSC, 1999b). Many of these types of systems that have to do with the way information from the environment is interpreted, manipulated and acted upon, are discussed in the following chapter concerning Intelligent Transportation Systems (ITS). The quality of driver education training is also an important factor, and has resulted in a number of new approaches such as graduated licensing, which is built upon the concept that driving tasks perform gradually more difficult and unrestricted.Generally, the majority of systems include three levels of tests, an initial provisio nal license, a preliminary licence, and a full licence (Englund et. al. , 1998). This form of graduated licensing has been shown to have a number of beneficial effects including a reduced risk for accident involvement (Smith, 1994). Inverted licensing, which encourages drivers to understand and accept responsibility for their actions has also been suggested (Klyve, 1998). Attempts to reduce accident risk through public safety campaigns and education programmes (e. . for school children) have often had a throttle long-term effect on traffic safety (see e. g. OECD, 1986 Jarmark, 1992 Linderoth & Gregersen 1994 Englund, Nyberg & Thiseus, 1997). Attempts to reduce accident severity for road users, particularly drivers and passengers of motor vehicles, has been the subject of a great deal of research by different vehicle manufacturers, particularly those who use the safety concept as an argument for marketing campaigns.The actual road user injury protection that has been developed as a result of large investments in in-vehicle design and research is discussed below in relation to vehicle engineering. For the safety of drivers and their passengers, the most important factor often concerns the use of injury protection measures rather than their provision. This is especially important with regard to the fact that many drivers consider themselves better than the average (Svenson, 1981 Williams, Peak & Lund, 1995). In many European countries, seat-belt use is relatively low resulting in an unnecessary number of fatalities and serious injuries.Many also fail to realise that the effectiveness of air bags is dependent on the use of seat belts (ETSC, 1999b). For unprotected road users the risk for (and consequences of) an accident can be reduced by ensuring easy detection by other road users through the use of suitably coloured clothing, reflexes, and cycle lights (OECD, 1998). Safety Improvements Through Vehicle Engineering Vehicle engineering has come a long way during t he past century, a fact that is reflected by the relatively small number of accidents that are directly attributable to vehicle failure.Modern vehicles undergo rigorous testing in order to ensure constancy and handling, adequate steering charact