The aim was to study the cause of the injuries of pedestrians when hit in frontal impacts by a vehicle. Depending on the impact speed, the type and severity of the injuries may be due partly to the vehicle and partly to the road/ infrastructure, when falling down. The study took into account the projection distance and the age of pedestrians.
The work has been supported by FSR (Fondation Sécurité Routière)
All the accident cases were reviewed by an expert committee composed by physicians and accident analysis experts. For each wounded pedestrian, the injuries were reviewed in order to determine their causing mechanism taking into account the accident occurrence circonstances, the vehicle deformations and the clues on the road or infrastructure.
The data base was a sample of 100 in-depth investigations and reconstructions of accidents from years 2009 to 2011 involving at least one injured pedestrian hit by a vehicle and continuously collected in a 20 km diameter area in the south of Paris (France). The accident analysis team was called with the emergency team on field where the data were collected.
In the sample, 89 pedestrians were injured in a frontal impact. For 83 of them, it was possible to evaluate the vehicle speed during the impact. In 12% of the cases the speed exceeded 50 km/h and all the pedestrians were severely injured (MAIS3+: pedestrian with at least one injury scored above AIS3) with a high projection distance. Therefore, we focused on frontal impact with vehicle speed below 50 km/h. In this configuration , considering injuries AIS2+, the head was the most often injured (53%) and then the lower limbs (21%). Among the wounding elements, the ground was incriminated in 27.5% of the cases, then the bonnet (22%), the windshield (17%) and the bumper (15.5%).When the vehicle speed was below 30 km/h, more than half of the injuries AIS2+ observed were caused by an impact with the ground. There was a compounding effect of age.
Though the sample is not representative of all French pedestrian accidents, it allows categorizing these accidents depending on the impact speed. For each speed range, the main causal factor of the injuries was determined.
The vehicle speed was the major factor in the determinism of the injury severity of pedestrians involved in frontal impact, firstly by direct impact secondly by increasing the projection distance and thus the severity of injuries due to ground impact. Primary safety systems should reduce the severity of pedestrian injuries by decreasing the impact speed.