From crash evidence to injury prevention: factors associated with injury severity in heavy vehicle crashes involving vulnerable road users in Pakistan.

Crashes involving heavy vehicles and vulnerable road users (VRUs) represent a serious public health challenge in low- and middle-income countries, where road traffic injuries contribute substantially to injury-related morbidity and mortality. However, the existing literature remains limited, as most studies focus on single VRU groups and are concentrated in high-income settings. As a result, little is known about injury severity in mixed-traffic environments such as Pakistan, where pedestrians, motorcyclists, and motorized rickshaw users interact with heavy vehicles under substantially different roadway and traffic conditions. To address this gap, this study investigates the factors associated with injury severity in crashes involving heavy vehicles and VRUs in Pakistan using 1,007 anonymized emergency-service crash records collected by Rescue 1122. A random parameters binary probit model with heterogeneity in means and variances was estimated to account for unobserved heterogeneity and variation in the effects of explanatory variables across crashes. The analysis indicates that male VRUs are less likely to sustain severe injuries, whereas VRUs aged 25 years or younger face a significantly higher probability of severe injury. Crashes occurring during weekends, at night, and under rainy conditions are associated with a higher probability of severe injury. Pedestrian and motorcyclist involvement, as well as distraction, are also associated with a substantially higher probability of severe injury in crashes involving heavy vehicles. In addition, primary roads, two- and three-lane roads, vertical curves, sidewalks, and access points are all associated with a higher probability of severe injury. The random parameter estimates further indicate that the effects of nighttime and distraction exhibit significant heterogeneity across crashes, with nighttime having a stronger effect in pedestrian-related crashes, at access points, and under rainy conditions. The results suggest the need for targeted interventions focusing on the protection of pedestrians and motorcyclists, younger road users, high-risk roadway environments, and context-sensitive enforcement and engineering measures on corridors with frequent heavy vehicle movement. These findings provide evidence to support injury prevention strategies, inform public health and transportation policies, and contribute to achieving safer and more equitable mobility systems in Pakistan and other low- and middle-income countries facing similar road safety challenges.