Improving Passing Lane Safety and Efficiency Grant uri icon



  • Passing lanes, in two-lane two-way rural highways, provide motorists with the opportunity to pass slow moving vehicles improving the level of service of the operations in these highways. Such passing maneuvers, however, can lead to hazardous situations for the passing vehicle as well as for the opposing traffic. Several head-on fatal and severe injury crashes occur in passing lanes in Idaho either at merge points (where passing maneuvers have continued too far) or just downstream of passing lanes where demand to pass is high. Field observations have shown that some vehicles, including large trucks and recreational vehicles, tend to increase speeds once in the passing lanes. This leads motorists to pass at excessive speeds that may carry into the merge area increasing the risk of a fatal or a severe injury crash. Passing lane safety and efficiency can be significantly improved if the lead vehicles with varying speeds were encouraged to be courteous and maintain a relatively slower speed allowing more vehicles to pass without excessive speeds or reckless weaving maneuvers. This project examines the effectiveness of two low-cost measures that have the potential of influencing the behavior of drivers while on the passing lanes. The two alternatives are: 1) improved signage upstream from and at the passing lanes and 2) alternative striping and lane marking.

date/time interval

  • January 1, 2013 -