Crash Injury Severity Analysis of Different Vehicle Types: Day-of-Week Differences

AbstractUsing five years of motor vehicle crash data from Shandong Province, China, vehicle types were divided into three categories—passenger cars, trucks, and motorcycles—to study the changes in factors influencing injury severity on workdays and non-workdays. Taking driver injury severity as the subject of study, three levels of crash injury severity were considered: no injury, minor injury, and severe injury. To capture potential unobserved heterogeneity, random parameters logit models with heterogeneity in the means and variances (RPL-HMV models) were employed for modeling. Three likelihood ratio tests were conducted to assess the transferability of model estimation results from workdays and non-workdays and from one vehicle type to other vehicle types. Subsequently, marginal effects were calculated to investigate the instability between the explanatory variables. The modeling results indicate that the estimated models are not transferable between different models on workdays and non-workdays and that there are differences in the factors affecting crash severity. Separate modeling is required between workdays and non-workdays, as well as between different vehicle types, because the influencing factors of each model are different. However, there were some variables such as male, age≥51 years, visibility at 50–100 m, proceeding straight, multivehicle crashes, national/provincial roads, urban roads, rural roads, no streetlights at night, and streetlights at night that showed relatively stable effects on the probability of injury severity for certain vehicle types on workdays and non-workdays. This study could provide a theoretical basis for traffic management departments to manage traffic safety for different vehicle types for workdays and non-workdays, helping to reduce the occurrence of severe crashes. Practical ApplicationsIn terms of driver characteristics. Passenger car, as well as motorbike, drivers aged≥51 years were involved in crashes, increasing the severity of injuries. To avoid severe crashes, the media could encourage drivers in this age group to drive less on non-workdays and to choose public transport for traveling. Traffic management authorities should also conduct regular driving skills tests and medical examinations for passenger car and motorbike drivers in this age group and recommend revocation of driver’s licenses and provisions of driver training and education for those who fail the tests. However, truck drivers aged≥51 years re