What causes severe truck crashes on the flat and mountainous expressways? A comparative study in China

The severity of collisions involving heavy trucks exhibits a difference between the flat and mountainous expressways. Based on 1,175 records of truck crashes from 2015 to 2020 on two typical expressways in China, a heteroskedastic ordered probit model was applied to determine the significant factors among driver-vehicle-roadway-environment interactions and their marginal effects on the collision severity outcomes. The modeling results demonstrated that some variables (i.e. speeding and risky following behaviors of drivers, existence of curves and downgrades, adverse weather, etc.) are significant predictors of truck crashes on both flat and mountainous expressways. In contrast, some variables were significantly correlated with truck crashes on only the flat expressway (upgrade section) or the mountainous expressway (involvement of multiple vehicles, truck’s overloading status, nighttime period). The findings, taken collectively, may be valuable as a reference for drafting traffic rules and implementing technical solutions to ensure a safer traffic environment for heavy trucks on expressways.