Abstract:
This study explores the effects of some of the key factors including roadway and
environmental characteristics, traffic-related attributes, crash-specific factors, emergency
response measures, and post-crash health conditions, on the Injury Severity Score (ISS) for
victims of Road Traffic Crashes (RTCs), 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) is 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 a significant correlation exists between PHT and ISS,
highlighting the critical need for rapid evacuation of crash victims to medical facilities.
The mode of evacuation emerged as a critical 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. Vulnerable road users (VRUs), such as pedestrians and
motorcyclists, exhibited higher ISS. Moreover, the study identifies that post-crash health
indicators like the Glasgow Coma Score (GCS), Respiratory Rate (RR), and Systolic Blood
Pressure (SBP) significantly influenced ISS, with lower values of these variables indicating
more severe injuries. 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 RTCrelated injuries and fatalities.
