Safety Evaluation of Advance Street Name Signs

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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. The objective of the pooled fund study was to estimate the safety effectiveness for several of the unproven, low-cost safety strategies identified in the National Cooperative Highway Research Program (NCHRP) 500 Series reports through scientifically rigorous crash-based studies. One of the strategies chosen to be evaluated for this study was advance street name signs at signalized intersections. This strategy is intended to reduce the frequency of older driver crashes and crashes related to way-finding (i.e., rear-end and sideswipe crashes) at signalized intersections. Geometric, traffic, and crash data were obtained at signalized intersections for 82 sites in Arizona, 65 sites in Massachusetts, and 46 sites in Wisconsin. 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 advance street name signs. Based on the aggregate analysis, sideswipe crashes were the only crash type that changed significantly, which was a 27% reduction in Massachusetts and a 10% reduction for the three States combined. While results showed an insignificant reduction for total crashes in Massachusetts and Wisconsin, there was an insignificant increase in total crashes in Arizona. For the three States combined, there was a statistically insignificant reduction in total crashes (1.6%). The disaggregate analysis indicated that advance street name signs may be more effective on the major road at three-legged intersections as well as those locations with a relatively large average annual daily traffic (AADT) or a large expected number of crashes. Also, additional signs (i.e., two or more per approach) were shown to be more effective than just one advance sign. Based on conservative cost estimates, a reduction of just 0.01 crashes per intersection-year would achieve a 2:1 benefit-cost ratio. Given the very low cost of this strategy and the potential to enhance way-finding, the use of advance street name signs is justified, particularly at three-legged intersections and locations with a relatively large AADT or a large expected number of crashes.