Pavement edge lines provide a visual guide in confining vehicles within the traveled lane. The 2000 Manual on Uniform Traffic Control Devices expanded the requirements of edge lines for rural arterials and collectors with narrow lane width. To address the question of whether the implementation of edge lines may have any negative safety effect on narrow rural two-lane highways, a study was conducted to investigate the distribution of vehicles' lateral position before and after edge line markings and to see if there is any potential reduction in crashes. The data were collected at seven tangent and three curved sections on Louisiana rural two-lane highways where the pavement width is less than 22-ft. The results clearly show that after the implementation of edge lines vehicles tended to move away from the pavement edge, which could lead to a reduction in run-off-road crashes -- the most common type of crash on narrow two-lane highways. The analysis also shows that even though the counts of centerline crossings increased at several sites during the daytime, the benefits of having the pavement edge line is significant at nighttime when the distribution of vehicles' lateral position is more centralized, which reduces the risk of having head-on and sideswipe collisions.
Abstract