Book Description

The Virginia Department of Transportation (VDOT) currently uses snowplowable raised pavement markers (SRPMs) to supplement longitudinal pavement markings on some facilities. SRPMs are much more visible than traditional longitudinal markings under wet, nighttime conditions. SRPMs have been reported to dislodge from pavement, however, which has raised the question as to whether alternative marking materials might be able to replace SRPMs. The purpose of this study was to investigate the visibility performance of longitudinal pavement marking materials currently on the market. The specific objectives of this study were (1) to determine whether or not new pavement marking materials could be used in place of SRPMs; (2) if SRPMs were to be used, to develop guidelines for their installation and maintenance; and (3) to determine the costs and benefits of using SRPMs to the maximum extent possible. No new data on the visibility or durability of pavement marking materials were collected for this study. The study primarily synthesized existing research on the characteristics of different marking materials and then applied information derived from the synthesis to Virginia-specific data to estimate the impacts of using different materials. National practices for installing, inspecting, and maintaining SRPMs were also reviewed. The results of the literature review indicated that SRPMs remain the only marking system that provides sufficient nighttime preview time at high speeds, especially under wet conditions. Further, SRPMs can improve safety in certain situations, but they can also degrade safety in other situations since drivers may travel at higher speeds when the distance they can see down the road at night increases. Proposed guidelines for the installation and maintenance of SRPMs were developed. They recommend that SRPMs be installed on all limited access freeways, on all two-lane roads with an average daily traffic volume above 15,000 vehicles per day, and on all roads with a posted speed limit of 60 mph or greater. Several other situations where SRPMs might be installed based on engineering judgment were also identified. A proposed maintenance schedule that requires inspections every 2 to 3 years was also developed. A conservative economic analysis indicated that the benefits of installing and maintaining SRPMs using the guidelines developed in this study outweighed the costs by more than 80 to 1, based purely on potential safety improvements on road geometries where SRPMs have been shown to improve safety. Further, VDOT can realize cost savings by discontinuing SRPM usage on low-volume facilities and by revising particular SRPM standards.