Impact of Edge Lines on Safety of Rural Two-Lane Highways

This report documents the results of the project for Impact of Edge Lines on Safety of Rural Two Lane Highways. This research project was initiated in the effort of compliance with the updated version of the Manual on Uniform Traffic Control Devices (MUTCD Millennium Edition, 2000) in the subject of edge line implementation in Louisiana. The objective of this study is to investigate if the marking of edge lines on rural narrow two-lane highways would result in any negative effect on drivers' behavior that in turn may debase highway safety. The before-and-after measurements show that: (a) edge lines help drivers confine their traveling path, particularly at night, and (b) edge lines have no or little effect on drivers' operating speed. Conclusively, this study found that the presence of edge lines has a positive impact and the magnitude of the impact is influenced by such factors as roadway width, operating speed, time of the day, frequency of heavy vehicles, pavement condition, roadway alignment, and traffic in the opposing direction. The results obtained from this project can serve as a guideline for implementation by transportation agencies in Louisiana for general conformance with the MUTCD on edge line markings for narrow rural roadways.