Many states have implemented truck lane restrictions in an attempt to improve safety and mobility on freeways. These restrictions typically prohibit trucks from traveling in the median (left-most) lane of multilane highways, which potentially increases passing opportunities and reduces negative interactions between slow-moving trucks and faster-moving vehicles. Virginia has restricted trucks from the median lane of some interstates with three or more lanes by direction since 1997, but no systematic evaluation of the safety impact of the restrictions has been conducted. Evaluations of similar restrictions in other states have yielded contradictory findings, but those studies often used a limited dataset. An Empirical Bayes analysis of Virginia’s restrictions was performed using 6 years of crash datafrom 22 sites with restrictions and 16 similar sites without restrictions. The analysis showed that a breakpoint in safety performance occurred around 10,000 vehicles per day per lane. Facilities where the volume was below this threshold had significantly fewer crashes than anticipated, averaging a 13 percent reduction in total crashes and a 32 percent reduction in fatal and injury crashes. Sites where the volume exceeded this threshold had increases in total crashes and fatal/injury crashes of 28 percent and 23 percent, respectively. A detailed analysis of crashes on the higher volume roads was conducted to screen out crashes where the restrictions likely played no role. That analysis showed that the number of truck-involved crashes was still significantly higher than predicted, indicating that safety on higher volume roads may be negatively affected by truck lane restrictions.
Abstract