Safety Effectiveness of “Stop Ahead” Pavement Markings

Abstract

There is a need for rigorous evaluation of low-cost safety strategies that states may implement as part of their strategic highway safety plans. Highway safety funds are limited, so it is important to identify cost-effective strategies. FHWA organized a pooled-fund study of 26 states to evaluate low-cost safety strategies; “Stop Ahead” pavement markings were one strategy selected for investigation. Geometric, traffic, and crash data were obtained for 175 intersections with “Stop Ahead” pavement markings in Arkansas, Maryland, and Minnesota. Similar data were obtained for reference sites within each state. An empirical Bayes approach was incorporated in a before–after study design to evaluate the safety effectiveness of the “Stop Ahead” pavement markings. An aggregate analysis indicated a significant reduction in total crashes for Arkansas, Maryland, and the two states combined. There was also a significant reduction in right-angle and rear-end crashes for Arkansas and a general reduction in injury crashes. A disaggregate analysis indicated that crash reductions are significantly greater at three-legged intersections than at four-legged intersections. The strategy was also more effective at intersections with all-way stop control. Given the low cost of this strategy, even with conservatively high cost estimates, only a modest reduction in crashes is needed to justify its use. On the basis of the estimated safety effectiveness, the necessary crash reduction is easily achievable.