Detailed assessment of pedestrian ground contact injuries observed from in-depth accident data

Most pedestrians struck by vehicles receive injuries from contact with the vehicle and also from the subsequent ground contact. However, ground related pedestrian injuries have received little focus. This paper uses 1221 German pedestrian collision cases occurring between 2000 and 2015 to assess the distribution and risk factors for pedestrian ground related injuries. Results show that for MAIS 2, the ground accounted for 24% of cases, for MAIS 3 the ground accounted for 20% of cases and for MAIS 4-5, the ground accounted for 14% of cases. There were no AIS 6 ground related injuries, though there were several fatal cases where the ground was coded as the most serious injury. The head, thorax and spine dominate AIS 4-5 ground contact injuries. Vehicle impact speeds were higher for ground related AIS 4-5 compared to AIS 2 injury cases and the average impact speed for ground related injuries to the upper and lower extremities was lower than for body regions like head, thorax and spine. There was a significant age effect on pedestrian ground related injury outcome, with older pedestrians suffering more severe injuries and the median age for thorax injuries was higher than for all other body regions. There was no significant difference in the proportions of AIS 2+ head injuries produced by ground contact for more recent vehicles (model year since 2005) compared to older vehicles (model year before 2005). However, logistic regression analysis showed that the normalised bonnet leading-edge height is a risk factor for adult pedestrian AIS2+ ground related head injuries, and this provides empirical support for recent computational modelling predictions which implied a relationship between vehicle shape and pedestrian ground contact injuries. Considering the potential benefits of preventing pedestrian ground contact, for collisions below 40 km/h two thirds of the injury costs would be eliminated if ground contact could be prevented, and even higher benefits are likely at lower speeds (20 and 30 km/h). These data demonstrate the importance of ground related pedestrian injuries and show that vehicle shape influences pedestrian injury outcome in ground contact. The data therefore provides significant motivation for countermeasures to prevent or moderate pedestrian ground related injuries.