Centerline Pavement Markings on Two-lane Mountain Highways: Volume 2

About the report:

The Virginia Department of Highways and Transportation uses a lane marking designated mountain pavement marking (MPM) on two-lane highways in mountainous areas. This special marking consists of a single broken yellow line supplemented with "PASS WITH CAUTION" signs. The standard Manual of Uniform Traffic Control Devices (MUTCD) passing and no-passing zones are not marked, with the result that passing maneuvers are not prohibited even when sight distances are inadequate for prevailing speeds. This practice has been criticized by the Federal Highway Administration, highway safety officials, and motorists. Consequently, the Research Council undertook a study to evaluate this centerline marking pattern. The evaluation adopted was made in the form of a before and after study. The before study entailed a literature review, a questionnaire survey of motorists and officials of other states, the recording of passing maneuvers at different sites using a movie camera, the collecting of data on traffic characteristics, and an analysis of accident data. The information obtained on passing maneuvers was then used to develop guidelines on minimum lengths of passing zones and minimum sight distances. The after study entailed the collection and analysis of data on passing maneuvers and traffic characteristics at sites marked with the MUTCD marking patterns based on the guidelines developed. It was determined that traffic characteristics do not significantly change when centerline markings are changed from MPM to the standard MUTCD marking and that the minimum passing zones and passing sight distances given in the MUTCD are inadequate for safe passing maneuvers. It was also determined that the minimum sight distances discretionally used in Virginia are too conservative. The data collected on passing maneuvers during the after study showed that the guidelines developed for minimum passing zones and sight distances are adequate for passing maneuvers on two-lane highways in mountainous areas.

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