In this paper, the causes of reduction in reflectivity of reflective raised pavement marker (rpm) and reflective raised traffic button (rtb) systems, and a procedure to evaluate the effectiveness of these two types of marker systems, are discussed. All marker systems lose 95 percent of their reflectivity in the first 6 months after installation. Approximately one-half (50 percent) of their initial brightness is lost in the first 25, 000 impacts and an additional 20 percent in the next 175, 000 impacts. The major cause of loss of reflectivity in rpms is the actual loss of the marker because of improper installation and the nature of the road surface on which the marker is placed. (Asphalt surfaces result in a greater loss of markers thanportland cement concrete surfaces.) Those markers that remain on the roadway lose reflectivity because of abrasion and moisture seepingbetween the lens and the reflector. The major problem of ceramic markers is loss of reflectivity. Ceramic button markers generally are not dislodged from the pavement surface because of their shape. The major losses of reflectivity for ceramic marker systems result from the loss of reflector units and dirt accumulation on the reflectors.A method for the maintenance of marker systems is presented that uses reflectivity and loss of markers as evaluating criteria. The procedure and criteria are applicable both to centerlines and lane lines. This paper appeared in transportation research record no. 1149, Visibility for highway guidance and hazard detection. For covering abstract see IRRD no 817811.
Abstract