Tram-pedestrian collisions: The severity of head injuries due to secondary impact with the surrounding infrastructure (ground)

The goal of the study was to conduct a series of tram-pedestrian collisions to assess the head injuries as the result of the secondary impact with the surrounding infrastructure (ground). The crash tests were conducted with an anthropomorphic test device for two collision scenarios: the initial frontal and side impact with a tram. Four tram types travelling at four different speeds (5 km/h, 10 km/h, 15 km/h, 20 km/h) were used. The primary outcome variable was the resultant head acceleration. The risk and severity of possible head injuries were assessed using the head injury criterion (HIC15). The results showed increasing head impacts with increasing speed for all tram types and collisions. The higher values of head acceleration were reached during the frontal impact (97–1677 g) compared to the side one (19–607 g). The HIC15 values showed a similar trend, exceeding the value of 1000 consistently during the initial frontal impact compared to the side one. This corresponded to a very high probability of AIS4+ injuries in the case of initial frontal impact. The secondary impact with the surrounding infrastructure was found more dangerous in the case of initial frontal impact, possibly resulting in more severe injuries. However, both collision scenarios showed much higher values compared to the primary impact between a tram and pedestrian.