Introduction:: As electric scooters have become more widespread, injuries related to their use have increased [1]. While generally mild injuries, 80% of instances where riders were killed were caused by vehicle collisions [2].
The objective of this study was to investigate the biomechanical causes of rider injuries in intersection vehicle impacts across a wider range of pre-impact conditions using finite element models (FE).
Materials and Methods:: To investigate scooter-car crashes, a previously developed e-scooter model was acquired [3]. The scooter rider was modelled with the Global Human Body Models Consortium (GHBMC) simplified 50th percentile male pedestrian model (M50-PS) which was positioned to mimic a typical e-scooter rider stance. Two publicly available and validated vehicle models were used to impact the rider, a sedan (FCR) and a sports utility vehicle (SUV). The original windshield models were rigid, but this would have created unrealistic rider-windshield interactions, thus, the windshield was made deformable. There were two primary types of intersection vehicle-rider impacts [4]. The first type was a vehicle traveling straight through the intersection and impacting a rider coming from the motorists’ right side which accounted for 31% of intersection collisions (Fig. 1 a). The second common crash type accounted for 29% of intersection collisions and was a motorist turning right at an intersection and a scooter again coming from the right of the motorist. Simulations were run until the rider model hit and rested on the ground. The probability of serious injury (AIS 3+) was calculated using injury outcomes from the head injury criteria (HIC), brain injury criteria (BrIC), neck injury risk (Nij), femur injury risk, and tibia fracture risk
Results, Conclusions, and Discussions:: All four impacts reported tibia and femur fracture (Fig. 1b). Three out of the four impacts reported low head and brain injury risks, but the straight SUV impact reported more substantial risks (head risk = 0.56, brain risk = 0.22). In three of the four impacts the head, brain, and neck reported low injury risks due to a lack of head-vehicle or head-ground contact. In these impacts the rider head never hit the vehicle, instead the rider rolled forward and separated from the vehicle. In addition, for these impacts the rider impacted the ground first with their legs and arms, breaking the fall and reducing the intensity of the head-ground contact. In two impacts the head never hit the ground due to the arms breaking the fall. This study simulated four vehicles to e-scooter impacts using a sedan and SUV across two different impact angles. The tibia and femur reported fracture in all four impacts, but the head, brain, and neck typically reported minimal injury risks. The primary cause of head and brain injury came from the head-ground contact which only occurred in one of the four impacts. This suggests that rider-ground protection should be the priority over rider-vehicle.
