Safety Impact of Edge Lines on Rural Two-Lane Highways

Pavement markings are an important part of the traffic control system, especially on rural two-lane roadways where these treatments often are the major traffic control measure. Compared to other types of longitudinal markings, the effect of edge lines on safety and driver behavior has been much less investigated. However, such markings may have a positive impact on the reduction of crashes on two-lane rural roads, as well as on the general comfort level of driving. This study compiled an inventory of rural two-lane highways under the operation of the Texas Department of Transportation (TxDOT), investigated typical dimensions and characteristics of such roadways, and utilized this information to perform a detailed accident statistic analysis. Crash statistics comparisons were made for highways with and without edge lines. In addition to general accident frequency analysis, varying traffic lane and shoulder widths, and roadway curvature, factors such as accident type, intersection presence, light condition, surface condition, crash-supporting factors, severity, driver age, and driver gender were considered. The research found that edge-line treatments on rural two-lane roadways may reduce accident frequency up to 26% and the highest safety impacts occur on curved segments of roadways with lane widths of 9 to 10 ft. In addition, edge-line presence shows some positive safety impact in reducing speeding-related accidents during darkness that may be related to better driver path and speed perception.