Background: Permanent raised pavement markers (PRPMs) were introduced for centerline and skip line application as a traffic safety measure to provide a more positive guidance for drivers in inclement weather and low-light conditions. These devices have been popular with highway agencies and have been widely used as supplemental delineation treatments to improve driver preview distances.

Recent studies in New York, Texas, and Pennsylvania have raised concerns about the relationship between PRPMs and crash rates. Specifically, the studies conducted in Texas and Pennsylvania indicated potential negative safety effects of these devices. In general, there have been few comprehensive and conclusive studies performed that quantify the safety effects of PRPMs.

There is a need to assess the safety effects of PRPMs and identify critical design parameters, such as selective versus nonselective application, lane demarcation versus edgeline, and sole use versus use supplemental to other pavement markings. The study shall encompass a representative sample of states' PRPM application experiences and shall document the traffic crash rates both before and after the installation of PRPMs at selected sites. In addition to identifying where and when PRPMs should be used to enhance safety, the research also needs to develop recommended design guidance.

Objective: The objectives of this research were to assess the safety effects of permanent raised pavement markers (PRPMs) and to develop guidance for their use. This research was accomplished by analyzing crash experience before and after installation of PRPMs using a comprehensive, statistically valid method for a representative sample of roadways in the United States.

Tasks: To accomplish the objective, the following tasks were conducted: (1) Conduct a literature search to identify safety-related studies of PRPMs. Evaluate the methodologies used and conclusions made to refine the focus and control/variables for this and future research efforts. (2) Using the results of the literature review, identify the critical variables and develop a comprehensive plan for conducting a safety evaluation of PRPMs. At a minimum, this plan shall include a rigorous multi-state analysis of crash data related to the effects of PRPMs, including controlling for variables such as geometry, environment, PRPM layout and application, and traffic and driver data. (3) Prepare an interim report. The interim report shall document the findings of Task 1 and include the comprehensive plan from Task 2. (4) Meet in Washington, D.C., with the project panel approximately 1 month after submittal of the interim report. Submit a revised interim report addressing the panel's review comments. The contractor shall not proceed with the remaining tasks without the approval of the NCHRP. (5) Execute the agreed upon option(s) of the plan. (6) Using the data collected in Task 5, develop guidance on the use of PRPMs. (7) Prepare a final report that documents the entire research effort, including a self-contained appendix that provides specific guidance on the use of PRPMs.

Status: The project has been completed.

Product Availability: NCHRP Report 518 presents the findings from this project.