A Case Study Approach to Understand Heavy Truck Safety-critical Events in Work Zones

Large trucks are overrepresented in work zone crashes. Data from the Federal Motor Carrier Safety Administration’s Large Truck and Bus Crash Facts show that, in 2017, 30% of work zone fatal crashes and 12% of work zone injury crashes involved at least one large truck, which was more than double the percentage of all crashes that occurred outside of work zones, where 12% of fatal crashes and 5% of injury crashes involved at least one truck. This study used data from four major truck naturalistic driving studies to investigate the risk associated with a variety of work zone roadway, environmental, and safety features. The vast majority of the work zone observations occurred with no adverse weather conditions present, dry road conditions, straight roadway alignment, and light traffic, with roughly three-quarters of commercial motor vehicle (CMV) drivers wearing a seatbelt. The most common features observed in work zones were warning signs, barrel barriers, and lane closures, which were used in various combinations. Traffic cones were associated with an increase of safety-critical event (SCE) risk, likely as a result of their small size and being less visible to CMV drivers. Reflective signs, barrels, and concrete barriers, however, reduced the SCE risk for CMV drivers in work zones by 40%–60%. There was a small decrease in SCE risk associated with light traffic in a work zone compared to moderate and heavy traffic. There was also a nearly 3-times greater risk of a CMV driver being involved in an SCE in work zones on single-lane roadways versus four-lane roadways. Active work zones had nearly twice the SCE risk for CMV drivers compared to inactive work zones. In active work zones, non-driving-related distractions, internal distractions, and external distractions all resulted in an almost three-fold increase in SCE risk for CMV drivers. When planning smaller, more temporary work zones, it may be beneficial for worker and road user safety if planners employ larger, more visible safety barriers such as barrels and reflective signage.