Safety Evaluation of Centerline Plus Shoulder Rumble Strips.

摘要

The Federal Highway Administration organized a pooled fund study of 38 States to evaluate low-cost safety strategies as part of its strategic highway safety effort. One of the strategies selected for evaluation was the combined application of centerline and shoulder rumble strips. This strategy is intended to reduce the frequency of crashes by alerting drivers that they are about to leave the travelled lane. Geometric, traffic, and crash data were obtained at treated two-lane rural road locations in Kentucky, Missouri, and Pennsylvania. To account for potential selection bias and regression-to-the-mean, an Empirical Bayes before-after analysis was conducted, using reference groups of untreated two-lane rural roads with similar characteristics to the treated sites. The analysis also controls for changes in traffic volumes over time and time trends in crash counts unrelated to the treatment. The combined results for all States indicate statistically significant crash reductions for all crash types analyzed. The crash type with the smallest crash modification factor (CMF) (i.e., the greatest crash reduction) is head-on, with a CMF of 0.632. Run-off-road and sideswipe-opposite-direction crashes have estimated CMFs of 0.742 and 0.767, respectively. For run-off-road, head-on, and sideswipe-opposite-direction crashes combined (i.e., lane departure crashes), the estimated CMF is 0.733. For all crash types combined, CMFs of 0.800 for all severities and 0.771 for fatal+injury were estimated. Intersection-related and animal crashes were excluded from the evaluation. Benefit-cost ratios were estimated to range from 20.2 to 54.7, depending on the treatment cost and service life assumption, which varied by State. These results are based on conservative service life assumptions.