Safety Evaluation of Improved Curve Delineation

FOREWORD The goal of this research was to evaluate and estimate the effectiveness of improved curve delineation on rural two-lane undivided roads as one of the strategies in the Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS), Phase II. This strategy is intended to reduce the frequency of crashes related to lack of driver awareness approaching curves as well as while navigating through curves by providing more conspicuous signing and lane markings. The safety effectiveness of this strategy has not been thoroughly documented previously, and this study is an attempt to provide an evaluation through scientifically rigorous procedures. However, the estimate of effectiveness for this strategy was determined by conducting scientifically rigorous before-after evaluations at sites where this strategy was implemented in the United States. The above safety improvement and all other targeted strategies in the ELCSI-PFS are identified as low-cost strategies in the The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document. Quality Assurance Statement The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. Development Contract Task Order Manager was Roya Amjadi. 16. Abstract 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 improving curve delineation. Geometric, traffic, and crash data were obtained at 89 treated curves in Connecticut and 139 treated curves in Washington to determine the safety effectiveness of improved curve delineation. Treatments varied by site and included new chevrons, horizontal arrows, and advance warning signs as well as the improvement of existing signs using fluorescent yellow sheeting. All sites were on two-lane rural roads. To account for potential selection bias and regression-to-the-mean, an Empirical Bayes (EB) before-after analysis was conducted. The aggregate results revealed an 18-percent reduction in injury and fatal crashes, a 27.5-percent reduction in crashes during dark conditions, and a 25-percent reduction in lane departure crashes during dark conditions. The reductions were more prominent at locations with …