Lane demarcation is conventionally accomplished by use of white traffic paint placed as a skip line. Most traffic paints are beaded by premixing glass beads in the paint, by drop-on applications, or a combination of the two. The retrodirective properties of the beads greatly enhance nighttime visibility during dry weather; however, visibility of the lines is practically nil during wet nighttime driving. Submerged beads cannot redirect the light when the need for guidance is mosL critical. Thermoplastic striping materials have been used to varying degrees of success by numerous agencies. Wet nighttime visibility of thermoplastics, as experienced in Kentucky, is generally far superior to that of conventional beaded paints. Thermoplastics are placed at a thickness of 125 mils and are thereby less likely to become submerged than conventional paints, which are placed at film thicknesses in the order of 14 mils and dry to approzimately 8 mils.

Late in 1965, the California Division of Highways reportedly issued a policy requiring the use of raised pavement markers as a replacement for most painted lines on future freeways and conventional highways. Other agencies have employed raised markers in various forms and have reported excellent to good wet nighttime visibility for markers remaining in place. Major disadvantages of the thermoplastics and raised markers are:

  1. they are quite expensive as compared to paint,
  2. they break or crack under traffic, and
  3. the present loss is high as a result of traffic and snow removal equipment.

In addition, the raised markers are rather difficult to install.

Christensen Diamond Services, Inc. of Salt Lake City, Utah, reportedly introduced the concept of grooving centerlines in an attempt to provide a rumble effect for alerting drivers straying outside their traffic lanes. It was later observed that the painted grooves were more visible at night during wet weather than were normal paint stripes. The concept of grooving and painting centerlines was thus promoted, and, as a result, several test sections were placed on Nebraska highways in the summer of 1968. In order to evaluate the effectiveness of grooving the centerline prior to striping, a section uf newly constructed pavement of I 71 in Carroll County, Kentucky, was chosen for an experimental installation. This interim report covers installation of the grooves and a preliminary evaluation of their value to date.

Report Date


Report Number

No. 282

Digital Object Identifier