Auto rickshaw impacts with pedestrians - A computational analysis of post-collision kinematics and injury mechanics

Motor vehicle-related pedestrian road traffic collisions are a major road safety challenge and a leading public health issue, since they are a primary cause of death and serious injury worldwide. In many developing countries, the auto-rickshaw–a three-wheeled vehicle with a canvas roof and side curtains – poses a significant risk to pedestrian safety due to the poor impact energy absorption of its structures and materials. This study presents a parametric and comparative analysis of auto-rickshaw-related pedestrian impacts and pedestrian-ground impacts by computational simulation, using a Finite Element model of an auto-rickshaw and LS-DYNA, 50th percentile adult male and six-year-old child Hybrid III Anthropometric Test Devices (dummies). The comparative study explored the kinematic responses and injury metrics associated with both adults and children impacted by an auto-rickshaw, as well as the most commonly impacted areas of an auto-rickshaw and the injury metrics for the adult pedestrian produced by primary and secondary impacts. The output data of the impact simulation was correlated against reported injury metrics, Head Injury Criterion, Neck Injury Criterion, Combined Thoracic Index, Injury Abbreviated Injury Scale and reported risk level. The results suggest that adult pedestrians are subjected to a relatively high risk of head, neck and chest injuries during primary impacts at 10, 20 and 35km/h, respectively, and some of the impact simulations suggest a risk of fatality. The 6YO-child pedestrians are at risk of serious head and neck injury at 10 and 15km/h, respectively. During secondary impacts, defined as impacts with a floor surface, head and neck injuries produced from ground contact are significant, including fatal injury, at 10km/h and greater, while insignificant chest injuries were observed at 40km/h. Vehicle impact response was investigated and Aluminium-6016-T4 and magnesium-AZ31B windscreen frame materials and a polycarbonate windscreen were found to produce the lowest injury risk of all the materials investigated whilst offering the greatest safety at the lowest cost. The present study provides valuable evidence for informing a series of recommendations and guidelines to make the auto-rickshaw safer during impacts with pedestrians. Overall, it has found that impact velocity, vehicle contact region, impact position and pedestrian size significantly influence the post-kinematic response of a pedestrian impacted by an auto-rickshaw and injury risk during primary and secondary impacts. Moreover, child pedestrians are subject to a relatively higher risk, compared to adults, during primary impacts. Secondary impacts were associated with a greater risk of head and neck injuries compared to primary impacts, even at low-impact velocities. Secondary impacts, however, produced much lower chest injury risk compared to primary impacts. Thus, even at relatively low impact velocities, the auto-rickshaw cannot be considered a ‘pedestrian friendly’ vehicle for use in urban areas. iii A b s t r a c t Future suggestions to reduce the injury risk level and increase the safety of the auto-rickshaw should be the implementation of strict safety regulations and, or, consideration of engineering solutions, such as retrofitting injury mitigation technologies to those auto-rickshaw contact regions which pose the greatest risk of producing pedestrian injury. In addition, modification of the frontal end geometry of the vehicle is recommended to ensure that injury risk is minimised during primary and secondary impacts