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Investigation of 184 passenger car–pedestrianaccidentsHui Zhao a , Zhiyong Yin a , Rong Chen b , Huipeng Chen c , Cui Song d , Guangyu Yang a &Zhengguo Wang aa Chongqing Key Laboratory of Vehicle Crash/Bio-Impact and Traffic Safety, Department4th , Institute of Surgery Research, Daping Hospital, Third Military Medical University ,Chongqing, 400042, Chinab Department of Radiology, Daping Hospital , Third Military Medical University , Chongqing,400042, Chinac China Automotive Technology & Research Center , Tianjin, 300162, Chinad Special Care World, Children's Hospital , Chongqing Medical University , Chongqing,400014, ChinaPublished online: 22 Jul 2010.

To cite this article: Hui Zhao , Zhiyong Yin , Rong Chen , Huipeng Chen , Cui Song , Guangyu Yang & Zhengguo Wang (2010)Investigation of 184 passenger car–pedestrian accidents, International Journal of Crashworthiness, 15:3, 313-320, DOI:10.1080/13588260903335290

To link to this article: http://dx.doi.org/10.1080/13588260903335290

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International Journal of CrashworthinessVol. 15, No. 3, June 2010, 313–320

Investigation of 184 passenger car–pedestrian accidents

Hui Zhaoa, Zhiyong Yina∗, Rong Chenb, Huipeng Chenc, Cui Songd, Guangyu Yanga and Zhengguo Wanga

aChongqing Key Laboratory of Vehicle Crash/Bio-Impact and Traffic Safety, Department 4th, Institute of Surgery Research, DapingHospital, Third Military Medical University, Chongqing 400042, China; bDepartment of Radiology, Daping Hospital, Third MilitaryMedical University, Chongqing 400042, China; cChina Automotive Technology & Research Center, Tianjin 300162, China; dSpecial

Care World, Children’s Hospital, Chongqing Medical University, Chongqing 400014, China

(Received 5 May 2009; final version received 14 September 2009)

In China, pedestrians were the most common and the most vulnerable of road users, meaning pedestrians were involvedin vehicle-pedestrian accidents more frequently. Little attention has been paid to the investigation of such accidents. Onesurveying group was built to randomly collect vehicle-pedestrian accidents and analyse these accidents from the vehicle–pedestrian crash characteristics and the relationships between the pedestrian injury outcome and the impact speed. 184pedestrians were injured and killed in these investigated passenger-car-pedestrian accidents. Among the 184 pedestriansinvolved in these accidents, 151 were crossing road arbitrarily (82.1%). There were only 17 accidents where the pavement andguardrail satisfied the safety standard. The males were the majority of the casualties (64.7%). Pedestrian injury localisationsin head, extremities, chest and torso accounted for 68.5%, 68.5%, 24.5% and 15.8%, respectively. Of the fatalities, 71.4%resulted from brain injury. The injury outcome in elderly pedestrians was more severe and the head severe injury proportionin children was more than that of an adult. Multiple injuries were common in pedestrians. The pedestrian injury outcomewas relative to the impact speed, i.e. faster the impact speed, higher was the pedestrian’s Injury Severity Score (ISS). Therewere no fatalities under the impact speed of 30 km/h and there were 4.4% of fatalities at the impact speed of 30∼39 km/h.When the impact speed was above 80 km/h, the pedestrians were severely injured or even killed.

Keywords: vehicle–pedestrian; accident; impact speed; pedestrian injury

1. Introduction

Road traffic accidents (RTA) have been a worldwide prob-lem, which has been a great threat for public health. Ac-cording to a recent study conducted by the World BankGroup [22], more than 1.17 million people die, and over 10millions are injured in RTAs each year around the world.The majority of these casualties, about 70%, occur in de-veloping countries. Pedestrians are the most vulnerable ofall road users because they are more frequently involved invehicle–pedestrian accidents. About 65% of the RTAs re-lated to fatalities in the world are from vehicle–pedestrianaccidents and the probability of pedestrians being injuredor killed is much higher than that for car occupants.

A greater percentage of the lower income populationtends to rely on walking as a primary mode of transporta-tion when compared with higher income group of popula-tion, which makes more people from lower income groupsexposed to vehicle–pedestrian crashes. In the United Statesin 2002, about 5000 pedestrians were killed and 71,000were injured owing to the car-to-pedestrian crashes [13].According to the Road Traffic Accident Annual CensusReport in China, about 378,781 RTAs occurred in 2006,which resulted in 431,139 and 89,455 injuries and fatalities,respectively [20]. It was also quoted that these accidents

∗Corresponding author. Email: zyyin@cta.cq.cn

caused 82,391 and 23,285 pedestrian injuries and deaths,which accounted respectively for 19.11% and 26.03% of theinjuries and fatalities related to RTAs. After surveying thevehicle–pedestrian accidents in Changsha, China, Li [10]suggested that the majority of vehicle–pedestrian crasheswere passenger car–pedestrian accidents.

Most advanced countries have done some researchon vehicle–pedestrian accidents through some projects onRTAs, such as the national accident sampling system inthe United States, Australia’s national crash in-depth studyand the accident investigation of Hannover in Germany.Some pedestrian characteristics involved in crashes, suchas age, gender, socio-economic status and behaviour, thatseem to have effects on vehicle–pedestrian crashes, havebeen studied in these projects. The traumatic injury surveil-lance, beginning with injuries by all causes, and followedby accident-related injuries, specifically pedestrian injuries,have been investigated from these databases. Recently, al-though there were some studies about vehicle–pedestrianaccidents in China, most of them were accident causesstatistics from some traffic administration departments[9, 26] or epidemiology analysis from hospitals’ emergencylogs and forensic examination records [11, 12]. Amoros[1] had suggested that, in general, the description and

ISSN: 1358-8265 print / ISSN: 1754-2111 onlineC© 2010 Taylor & Francis

DOI: 10.1080/13588260903335290http://www.informaworld.com

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314 H. Zhao et al.

classification of RTAs were significantly different from thestudy background of departments because of their variedstudy focus. Therefore, some characteristics of vehicle–pedestrian accidents have not been clearly understood fromthe studies published in China.

In China, there are five types of roads: national roads,province roads, county roads, highways and urban roads.For different types of roads, the population and vehicle vol-ume are different. The characteristics of vehicle–pedestrianaccidents on different types of roads are seldom understood,which is very important if some measurements to preventvehicle–pedestrian crashes are to be put in place. What’smore, it has not been clearly understood that weather androad conditions affect vehicle–pedestrian crashes. In China,the relationship between the vehicle impact speed and thepedestrian injury outcome has not been clearly understood.Therefore, vehicle–pedestrian accidents should be investi-gated in more detail.

The objective of this analysis is to determine vehicle–pedestrian crash characteristics and the relationships, ifany, between the pedestrian injury outcome and the impactspeed. Specifically, this study aims to examine age differ-ences in pedestrian crashes with respect to injury severity.To do this, we examined pedestrian injury and several effectfactors on vehicle–pedestrian crashes, such as weather, roadcondition and pedestrian behaviour, by randomly surveyingthe vehicle–pedestrian accidents in Chongqing, Shanxi andBeijing provinces of China. These findings may aid in theplanning of environments that are conducive to safe pedes-trian activity. The results of this study should help guidesafety policy decisions to ensure the well-being of pedes-trians.

2. Methods and material

2.1. Survey group and accident source

An accident survey group including researchers, engi-neers and medical experts was built to investigate thevehicle–pedestrian crashes. The group randomly collectedthe vehicle–pedestrian accident details containing informa-tion about humans, vehicles and circumstances from theprovinces of Beijing, Shanxi and Chongqing between 2006and 2008 by adopting the following procedure.

A form was designed to document the crash data includ-ing time, weather, road categories, road conditions, vehicleshape, pedestrian’s age, gender, type of trauma, localisa-tions of wounds, injury severity and outcome, and state-ments by the driver and the witness. The survey groupmember filled the forms with crash data. The vehicle–pedestrian accidents meeting the following requirementswould be chosen and analysed.

2.2. Accident-inclusion standard� The vehicle involved in the pedestrian crash should be a

passenger car.

� The pedestrian injury should be recorded in detail andAbbreviated Injury Score (AIS) should not be less than1.

� The accident documentation should include detailedsketch of the field.

� The contact marks on the car causing pedestrian injuryshould be included in the accident document.

2.3. Pedestrian age and pedestrian injury group

The pedestrians involved in the surveyed crashes were di-vided according to age into the following five groups: groupI (0–15 years), group II (16–28 years), group III (29–44years), group IV (46–64 years) and group V (above 64years).

The accident outcomes were divided into three groups:slight injury (maximum abbreviated injury score or MAIS< 3), severe injury/non-fatal (MAIS ≥ 3) and fatality.

2.4. Impact speed estimation

In some accidents, where some evasive action, typicallyemergency braking, was attempted by the drivers so thatthe emergency braking skid marks were left on the accidentfield or the pedestrian throw distance could be measured, theimpact speed could be estimated according to the brakingskid marks or the pedestrian throw distance by the followingequations [16]:

v =√

2as, (1)

where a is the deceleration and s is the braking skid dis-tance, and

v =√

2g × ϕ ×(√

h + x

ϕ−

√h

)× 3.6, (2)

where ϕ is defined as the friction coefficient between pedes-trian and road, x is the pedestrian throw distance and h isthe height of the pedestrian’s centre of gravity.

In other accidents without some material evidence, suchas braking skid marks and pedestrian throw distance, theimpact speed could be evaluated according to the headwrap-around distance (WAD) by simulating the vehicle–pedestrian crash with MADYMO

©R[18, 24].

2.5. Statistical analysis

The non-parametric tests were used to perform statisti-cal analysis with the SPSS

©Rsoftware package (SPSS Inc,

Chicago, IL). Data were expressed as mean ± standard er-ror of mean (SEM) and p-value of 0.05 was consideredstatistically significant.

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International Journal of Crashworthiness 315

Table 1. Pedestrian casualties statistics.

Male Female

Age group Average age Slight injury Severe Injury Fatality Average age Slight injury Severe injury Fatality

I 7.5 ± 3.9 6 5 1 10.5 ± 6.4 0 2 0II 20.4 ± 2.0 8 10 0 20.6 ± 2.1 6 2 1III 36.0 ± 4.6 14 24 3 35.6 ± 4.8 10 9 3IV 53.8 ± 5.1 11 18 4 56.2 ± 5.3 9 9 4V 75.3 ± 6.8 5 5 5 72.9 ± 5.8 4 2 4

3. Results

3.1. Accident description

Of the collected data on vehicle–pedestrian accidents, 184cases (30 in Beijing, 20 in Shanxi and 134 in Chongqing)meeting the analysis’ inclusion requirements were chosenand investigated. In these accidents, 184 pedestrians werekilled or injured. The majority of these accidents (160) oc-curred on a sunny day, which accounted for 87%. Of theseaccidents, 81% occurred on urban roads. There were 17accidents on the roads, which met pavement and guardrailsafety standards and accounted for only 9.2% of the totalsurveyed accidents. The accidents that occurred on straightroads accounted for 84.2%, and 10.8% occurred on cross-roads. Of the casualties, 151 pedestrians (82.1%) werecrossing the road, 21 pedestrians (11.4%) were walkingalong the road and 12 pedestrians (6.5%) were on the roadplaying or working prior to the crash.

3.2. Pedestrian casualties

Of the 184 killed or injured pedestrians, there were 119males and 65 females. The youngest was 2 years old, andthe oldest was 85 years. Table 1 shows general descriptivestatistics of the population involved in the crashes being

analysed in this study. The pedestrians that had slight injury,severe injury and fatality were 73, 86 and 25 respectively.According to the data, only 14 pedestrians aged 0–15 yearswere sampled, which occupied 7.6% of the casualties. Themaximum casualties were in group III (34.2%), meanwhile,fatalities in group V (36%) were more than in other groups(x2 = 12.378, p < 0.001). The proportion of severe injurieswas 44%, 52% and 49.1%, and that of fatalities 3.7%, 9.5%and 14.5% in groups II, III and IV respectively. The injuryseverity did not show statistical difference among groupsII, III and IV.

3.3. Kinematics of the pedestrian injury

The sources of injuries to various body organs, where thecontact marks were observed, were distributed on the wind-screen, A-pillar, bonnet, bumper and external vehicle com-ponents. One typical car–pedestrian crash was shown inFigure 1, where the first contact occurred between thebumper and the leg and knee-joint area when the pedestrianwas crossing the road, followed by thigh-to-bonnet edgecontact. Relative to the car, the pedestrian’s lower extrem-ities were accelerated forward and the upper body rotatedand accelerated backwards. Consequently, the pedestrian’spelvis and thorax were impacted by the bonnet edge and top,

Figure 1. Simulation of one typical car–pedestrian crash.

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Table 2. Statistics of pedestrian injury localisations and severity.

Head (AIS) Thoracic (AIS) Abdominal (AIS) Extremities (AIS)

Age group 1–2 3–4 5–6 1–2 3–4 5–6 1–2 3–4 5–6 1–2 3–4 5–6

I 1 7 0 1 1 0 1 0 0 6 2 0II 6 6 1 0 4 0 3 3 0 15 5 0III 11 26 5 5 15 0 5 4 0 32 9 0IV 20 19 5 8 8 0 5 3 0 30 6 0V 6 12 1 1 2 0 3 2 0 14 7 0

respectively. Finally, the second injury on the pedestrian’shead was caused when the pedestrian fell on the ground.Road and roadside objects were also the common source ofinjury to the head in this survey.

Environment

Crash field: Straight urban road with limited travellingspeed of 60 km/h, no braking skid marks, with-out pavement and guardrail.

Car: The contact area located on bumper, bonnetand windscreen.

Humans involved

Driver: Declared driving speed, about 60 km/h.Pedestrian: Man, 43-year old, height 1.74 m, mass

70 kg, crossing the road on the estimatedposition.

Injury outcome: Deceased, skull fracture, severe brain in-jury, the left ribs fracture, fracture of theleft femur.

Simulation

The pedestrian’s lower extremity accelerated forward andthe upper body rotated and accelerated backward, the coin-cident head WAD at the impact speed of 68 km/h.

3.4. The characteristics of pedestrian injuries

The pedestrian’s head, neck, chest, abdomen, extremitiesand spine were common localisations of wounds in thisstudy. The head, extremities, chest and abdomen injuries

were the most common, which occupied 68.5%, 68.5%,24.5% and 15.8% respectively. The injury localisation andseverity in different age groups are shown in Table 2. Thenumber of head AIS3+ was up to 7, which accounted for50% of the severe head injuries in group I and was obviouslymore than the others.

Multiple injuries were common among the fatalities, se-vere injuries and slight injuries, with a proportion of 76.0%,66.3% and 42.5% respectively. The main cause of pedes-trian fatalities was brain injury, which occupied 71.4%, ashas been shown in Table 3.

3.5. The pedestrian injury outcomes at the variedimpact speeds

The crashes occurred on highways at the highest impactspeed of 70.9 ± 27.4 km/h on average. The average carimpact speed on urban roads was 39.7 ± 14.9 km/h. Therewere 128 crashes when the car impact speed was 20–59km/h, which occupied 85.9% of the total crashes on urbanroads.

Results have shown that impact speed influenced sig-nificantly the pedestrian injury outcomes (p < 0.001). Asshown in Figure 2, the slight and severe injuries were 13and 21 without fatality, when the impact speed was un-der 30 km/h. On the other hand, when the speed was be-tween 30 km/h and 39 km/h, the fatalities, severe injuriesand slight injuries were 2, 15 and 29, which accounted for4.4%, 32.6% and 63.0% respectively in 46 cases; when thespeed was between 40 km/h and 49 km/h, the fatalities,severe injuries and slight injuries were 7, 20 and 14 with aproportion of 17.1%, 48.8% and 34.1% respectively in 41cases; when the speed was between 50 km/h and 59 km/h,

Table 3. Statistics of multi-injuries.

Head (AIS) Thoracic (AIS) Abdominal (AIS) Extremities (AIS)

Multi-injuries 1–2 3–4 5–6 1–2 3–4 5–6 1–2 3–4 5–6 1–2 3–4 5–6

Slight injury 31 31 0 0 9 0 0 10 0 0 58 0 0Severe injury 57 12 58 1 4 23 0 5 7 0 28 22 0Fatality 23 1 12 11 2 7 0 2 5 0 11 7 0

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International Journal of Crashworthiness 317

Figure 2. Impact speed and pedestrian injury outcomes.

the fatalities, severe injuries and slight injuries were 1, 23and 7 with a proportion of 3.2%, 74.2% and 22.6% respec-tively in 31 cases; when the speed was between 60 km/hand 69 km/h, the fatalities, severe injuries and slight injurieswere 3, 11 and 1 with a proportion of 20.0%, 73.3% and6.7% respectively in 15 cases; when the speed was between70 km/h and 79 km/h, the fatalities, severe injuries andslight injuries were 7, 3 and 1 with a proportion of 63.6%,27.3% and 9.0% respectively in 11 cases; when the speedwas above 80 km/h, all pedestrians were severely injured oreven killed, and finally, when the speed was above 90 km/h,all pedestrians were killed.

Table 4 shows the car impact speed influence on thepedestrian injury severity scores (ISS). As the impact speeddiscrepancy was 10 km/h, ISS has no differences statisti-cally. As the discrepancy was 20 km/h, ISS shows differ-ences significantly. When the impact speed was between20∼29 km/h, the ISS in the group IV was higher evidentlythan that in the group II.

4. Discussion

Weather was one of the main factors causing the roadtraffic accidents. The vehicle brake system did not workeffectively in wet road conditions and the car driver was not

Table 4. Pedestrian ISS at impact speed range of 20 to 59 km/h.

Total I II III IV VImpact speed

(km/h) n ISS n ISS n ISS n ISS n ISS n ISS

20–29 25 7.7 ± 5.5∗∗ 1 9.0 5 3.4 ± 1.8∗ 5 7.2 ± 7.3 13 9.3 ± 5.5∗ 1 9.030–39 46 8.6 ± 7.1�� 4 9.5 ± 4.9 8 6.4 ± 5.5 19 7.4 ± 5.8 8 9.5 ± 7.6 7 13.0 ± 11.440–49 41 14.8 ± 10.2∗∗ 3 12.7 ± 11.0 5 14.6 ± 6.0 13 17.0 ± 14.3 13 14.4 ± 8.9 7 12.7 ± 6.450–59 31 15.3 ± 6.3�� 3 12.7 ± 7.6 4 14.5 ± 8.1 10 19.0 ± 5.0 10 13.3 ± 5.3 4 12.0 ± 6.0

∗p < 0.05; ��,∗∗p < 0.01.

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able to recognise danger prior to collision when the visi-bility was affected on a rainy day. Therefore, the RTAs, ingeneral, occurred more frequently when the weather wasbad. More people went out walking instead of driving inChina due to its low level of mobilisation and hence therewere more pedestrians on a sunny day than on a rainy day.More pedestrians came out and there was a higher prob-ability that vehicle–pedestrian crashes would occur whenthe weather was sunny. That is why more passenger–car–pedestrian crashes occurred on any sunny day than on arainy day [4]. On the other side, the higher road densitiesand pedestrian exposure level in the urban areas, with highpopulation and more commercial accessibilities, would re-sult in more vehicle–pedestrian crashes. Chalabi suggestedthat decreasing 15% of vehicular volume would prevent14% of injuries and 25% of fatalities [2]. From this study itis evident that more passenger –car–pedestrian crashes oc-curred on urban roads than on any other category of roads,which suggested that the car–pedestrian crash preventiondomains should be focused on the urban roads.

It was also important to consider pedestrian behavioursbecause a large number of pedestrian accidents may beattributed to improper pedestrian behaviours, such as al-cohol consumption, mid-block crossing and crossing theroads arbitrarily. In this research, 82.1% of accidents werecaused by pedestrians crossing or disobeying the traffic sig-nal; the proportion was higher than that of 76% by Yuan[25] and 71.4% by Zhou [26]. It also suggested that ed-ucation about traffic safety should be improved in Chinaso that the pedestrians could avoid improper behaviours.Pedestrians walking in the zones where the pavement andguardrail did not meet safety standards would indulge insome type of risky behaviours, such as crossing arbitrar-ily, walking in mid-block or even staying in mid-block.Therefore, these sections of roads were inclined to the oc-currence of vehicle–pedestrian accidents [26]. Conversely,the vehicle–pedestrian accidents would decrease if the roadconstruction met the safety requirements, which only ac-counted for 9.2% of all surveyed accidents in our study.Therefore, it is important for the traffic administration de-partment to build pavements, pavement guardrail, pedes-trian bridges and underways for preventing pedestrians fromcrossing the roads arbitrarily; these steps could be effectivein bringing down the vehicle–passenger accidents.

Pedestrians’ age and gender were also among thepedestrian characteristics that seem to have an effect onpedestrian–vehicular crashes besides their socio-economicstatus. For example, children usually committed critical er-rors such as running across the street because they tendedto be less educated about safety rules and the elderly wereinvolved in crashes because they had slower response timesand decreased ability to recognise dangerous situationswhile walking or crossing the road. Mental confusion andsensory changes, such as hearing and visual loss, may placeelderly pedestrians at a disadvantage. As China is an ad-

vancing country with a low level of mobilisation, therewere more adult pedestrians than elderly (above 65 years)and children (under 16 years) because walking was con-sidered to be an important mode of transportation, so thecasualties of adult pedestrians, especially aged 29–44 years,were maximum in our research. Men tended to engage inmore risk-taking behaviours than women and therefore weremore susceptible to being involved in crashes [9, 10, 26].

From the kinematics of the adult pedestrian injuries, thefirst contact occurred between the bumper and either theleg or the knee-joint area, followed by thigh-to-bonnet edgecontact. Relative to the car, the pedestrian’s lower extremitywas accelerated forward and the upper body was rotated andaccelerated. Consequently, the pedestrian’s pelvis and tho-rax were impacted by the bonnet edge and top, respectively.Finally, the second injuries were caused when the thrownpedestrian fell and contacted the ground. The pedestrianhead, neck, chest, abdomen, extremities and spine were in-jured during these crash processes, which resulted in mul-tiple injuries. Our study was in agreement with other pub-lished data, that chest and abdominal injuries are relativelyless common than either head or extremities injuries [17].The pedestrian’s head injury usually had the worst neuro-logical outcomes in vehicle–pedestrian crashes comparedto other types of road accidents, which was one of the mainfactors that resulted in pedestrian fatalities [6], accountingfor 71.4% in our study. Yanar [23] demonstrated by study-ing 8401 pedestrian injuries caused by automobiles thatpatients with the severe head injuries (AIS > 3) were sig-nificantly more likely to have cervical spine injuries (CSI)than less severe head injuries (AIS ≤ 3) (1.3% versus 9.0%,p < 0.0001).

The severity of pedestrian head injury was relative tothe vehicle impact speed and the head impact locations onthe vehicle. The head impact locations on the vehicle weredetermined by the impact speed, the pedestrian’s height [25]as well as vehicle profiles. The locations of the most serioushead injuries were adjacent to the windscreen, the base ofthe windscreen as shown in Figure 1, the edge of the hoodand the A-Pillar. These head impact locations were beyondthe limit of the adult head form test area, suggesting thatthese structures should be considered for pedestrian’s headprotection.

In addition, age and gender played an important role inthe anatomic distribution and injury severity and survivaloutcomes after the crash. In children, their heads wouldmake contact with the car bonnet edge because of theirshorter stature and their skull being soft, so head injuries inchild pedestrian were more severe than in the adult pedes-trian. The European Enhanced Vehicle-Safety Committee(EEVC) found by surveying 321 child pedestrian accidents[3] that 36% of the registered AIS1+ injuries and 72% ofthe AIS4+ injuries were head injuries. An accident inves-tigation conducted by International Harmonized ResearchActivities (IHRA) showed that head injury occupied 41%

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of AIS2+ injuries in child pedestrian accidents [5]. Theproportion of severe injury and fatality among females islittle more than in males; however, Starnes et al. consideredthe days of hospitalisation of males lasted longer than thatof females [19].

Impact speed was one direct factor relative to pedestrianinjury outcomes besides the car frontal structure, pedestrianage and gender. The conclusion that the faster the impactspeed, more severe would be the injury has been docu-mented in a number of studies about vehicle–pedestriancrashes. Pasanen [14], for example, concluded from threestudies relating to impact speed and pedestrian injury sever-ity that about 5% of pedestrians died when the impact speedwas up to 20 mph, about 40% died when the speed was 30mph, about 80% died when the speed was 40 mph, andnearly 100% were killed when the speed was over 50 mph.An estimate of pedestrian injury outcome at a given impactspeed was also performed in our research. There was nofatality if the car impact speed was under 30 km/h; 4.4%fatalities at the impact speed of 30–39 km/h and 17.1%fatalities at the impact of 40–49 km/h. All sampled pedes-trians were either severely injured or killed when the impactspeed was above 80 km/h. All pedestrians died when theimpact speed was over 90 km/h in this study. In the caseof severely or fatally injured, pedestrians would die if theywere not treated competently in time. That is why the in-cidence of fatal injuries was higher for impact speeds of40–49 km/h and 70–79 km/h, while it was lower for thein-between groups in the limited samples. The conclusionthat the incidence of slight injuries would decrease with theincrease of impact speed could be drawn.

At the same impact speed, the proportion of fatalitiesin truck–pedestrian crashes would be higher than that incar–pedestrian crashes [8]. Therefore, the pedestrian in-juries were more severe if the truck wasn’t excluded inthe previous studies. Karger [7] thought that primary andsecondary injuries did not show a relationship to impactspeed and the occurrence of four types of indirect injuries,i.e. spinal fractures, ruptures of the thoracic aorta, inguinalskin ruptures and dismemberment of the body, revealeda clear relationship to the impact speed. He found that ifthere were no spinal fracture, the speed was below 70 km/hand probably below 50 km/h, and aortic and inguinal skinruptures were always present if the speed was above 100km/h but never occurred below 50–60 km/h, and if dis-memberment occurred, the speed was above 90 km/h [7].An estimation of the impact speed from the presence orabsence of indirect injuries could be performed in futureworks.

Our research showed that the crashes with impact speedmainly distributed at the range of 20–59 km/h, at the av-erage speed of 39.7 ± 14.9 km/h, which accounted for85.9% of all crashes on urban roads. Yuan [25] suggestedthat 28% of the car impact speed injuries were at a speedof 30–40 km/h on urban roads. In fact, the car’s travelling

speed was obviously over the impact speed, so overdriv-ing has been a predominant factor contributing to RTAs.However, small reductions in travelling speed were likelyto result in large reductions in impact speed and stoppingdistance in vehicle–pedestrian crashes, often to the extentof preventing the collision altogether. Wazana et al. [21],in a meta-analysis, found that higher speed limits were as-sociated with higher risk of injuries to child pedestrians instudies in New Zealand and Seattle, Washington. Pitt et al.[15] examined about 1000 urban crashes with pedestriansyounger than 20 years of age taken from NHTSA’s Pedes-trian Injury Causation Study (PICS) data. They found that,compared to crashes with vehicle travel speeds of 10–19mph, the risk of serious injury (or death) was 2.1% forspeeds of 20–29 mph, 7.2% for speeds of 30–39 mph and30.7% for speeds of 40 mph or more. Therefore, the speedlimit was necessary in the urban areas with high population,especially children.

AcknowledgementsThis work was supported by the National Key Research and De-velopment preliminary Plan of China (2007CB516704) and Na-tional Natural Science Foundation of China (30800243, 60771025,30670513).

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