How mode of evacuation, roadway environment, and traffic conditions relate to injury severity score? Untangling the role of pre-hospital time in road crashes

This study explores the effects of some of the key factors, including emergency response measures, roadway and environment, traffic-related attributes, and crash-specific factors, on the Injury Severity Score (ISS) of Road Traffic Crashes’ (RTCs) victims, both directly and through pre-hospital time (PHT), using rigorous path analysis. Data for 298,654 crashes, compiled by the Road Traffic Injury Research and Prevention Center (RTIRPC) in Karachi (Pakistan), were used for analyses. Owing to the corner-solution distribution of the response variables (PHT and ISS), two Tobit regression models are estimated after accounting for missing values through synthetic data generation. Marginal effects from these models are used in the path analysis. The findings suggest that ISS increases by 0.01 units with a unit increase in PHT, highlighting the critical need for rapid evacuation of crash victims to medical facilities. The mode of evacuation emerged as a crucial factor, with ambulances resulting in increased PHT and ISS compared to private or public transport, underscoring the improvement needed in the dedicated ambulance-based emergency response. PHT and ISS were found to be higher in nighttime crashes, necessitating better emergency medical services (EMS) response during the night. Intersection crashes were associated with lower PHT and ISS; whereas, crashes on undivided roads and those involving multiple or large vehicles increased PHT and ISS. The path analysis revealed that the overall effects of some of the key variables on ISS were higher than their direct effects – something that could not be explored without the path analysis. These insights can help policymakers develop strategies to improve emergency response and road safety, ultimately reducing the number of RTC-related injuries and fatalities.