Determinant of injury severities in large truck crashes: A weekly instability analysis

In the past, many attempts have been made to study the effects of large trucks on the safety of roadway users. However, the exact effects of weekdays and weekends on the injury-severity of these types of crashes are lacking. In this study, crash data from Los Angeles was used to investigate the transferability of the large-truck crash injury-severity determinants across weekdays and weekends. Crash-injury severities were estimated using random parameters logit models while considering three categories of injury-severity levels. The model estimation was done by considering several parameters that could potentially affect the crash injury severities such as truck's characteristics, drivers' attributes, driver actions, weather conditions, crash time, and roadway attributes. The transferability of the model estimation results across weekdays and weekends was assessed using likelihood ratio tests. Moreover, the stability of the explanatory variables was investigated using the calculated marginal effects. With a high confidence level, the estimation results disclose that weekday/weekend must be modeled separately as the contributing factors to each model are different. Still, some factors such as young drivers, at fault drivers, rear-end crashes, colliding fixed objects, intersection related crashes, and crash time are affecting injury severity in both models. The findings of this research could be used by trucking companies and decision makers to better regulate the traffic or trucking rules for weekdays and weekends.