The Federal Highway Administration (FHWA) organized a Pooled Fund Study of 26 States to evaluate low-cost safety strategies as part of its strategic highway safety effort. One of the strategies chosen to be evaluated for this study was STOP AHEAD pavement markings. This strategy is intended to reduce the frequency of crashes related to driver unawareness of stop-control at unsignalized intersections. Geometric, traffic, and crash data were obtained at unsignalized intersections for 8 sites in Arkansas, 9 sites in Maryland, and 158 sites in Minnesota. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before-after analysis was conducted to determine the safety effectiveness of installing STOP AHEAD pavement markings. Results of the aggregate analysis indicate a statistically significant reduction in total crashes for Arkansas, Maryland, and the two States combined. The combined aggregate analysis indicates that at least a 15-percent reduction in total crashes can be expected conservatively. There is also a statistically significant reduction in right-angle and rear-end crashes for Arkansas. A reduction in injury crashes is shown for Arkansas and Maryland and is statistically significant at the ten percent level for the two States combined. The results for Minnesota were not included in the main analysis, but support the conclusion that this strategy is safety effective. The disaggregate analysis indicated that crash reductions are highly significant at three-legged intersections and significantly greater than reductions at four-legged intersections. The strategy was also more effective at intersections with all-way stop-control (AWSC). Given the low-cost of this strategy, even with conservative assumptions, a modest reduction in crashes is needed to justify their use. Based on the estimated safety effectiveness of STOP AHEAD pavement markings, the necessary crash reduction to obtain a 2:1 benefitcost ratio is easily achieved. Therefore, this strategy has the potential to reduce crashes cost-effectively at unsignalized intersections, particularly at three-legged and AWSC intersections. (Author/publisher)
Abstract