Even though a large number of potentially hazardous locations exist on rural, two-lane roads, guidelines have not been developed for use of raised pavement markers under night and during adverse weather conditions. The purpose of this study was to evaluate the use of raised markers at a sharp curve and narrow bridge in Kentucky. Visual observations, speed data, encroachment data, and accident data were used to evaluate the effectiveness of the markers.

Extensive visual observations of the sharp curve and narrow bridge in this study have provided data to support recommendations for improved delineation at similar sites on rural, two-lane and four-lane roads. The best delineation found for sharp curves is to place raised markers on the centerline at 40-foot (12.2-m) spacings. At narrow bridge sites (bridge width less than approach width), raised markers should be placed at a decreasing spacing when approaching the bridge. The number of markers required and the location at which they should begin were also determined. A delineation improvement program for narrow bridges and sharp curves involving raised markers would mainly apply to rural areas. Snowplow damage could make use of conventional markers impractical.

Report Date


Report Number

No. 522

Digital Object Identifier



The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Bureau of Highways or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.