Evaluation Of Snowplowable Raised Reflective Pavement Markers PDF Download

A commonly used method to delineate lane lines on Virginia's highway pavements is a combination of reflective tape and snowplowable raised pavement markers (SRPMs). The SRPM system consists of a reflective lens epoxied into a plow deflector. The deflector is typically an H-shaped protective steel or cast-iron casting that consists of a pair of parallel keels and a connecting web. The entire system weighs approximately 6 pounds. While this arrangement is thought to improve the visibility of lane lines during darkness and inclement weather, there are questions as to whether the SRPMs can become damaged or detached from the pavement after prolonged exposure to traffic and snowplows. In Virginia, there is no formalized method or schedule for routinely inspecting these markers. They are often examined only when repaving or restriping is scheduled. In April 2006, a SRPM fragment went through the windshield of a van traveling on I-95 in Prince William County, striking a passenger. In response to this incident, a statewide study was initiated to determine if there were any potential problems with SRPMs becoming damaged or detached on Virginia's interstates. Casting condition, reflector condition, epoxy condition, and installation adequacy were inspected on 78 1-mile segments of interstate pavement containing SRPMs. The focus of the study was on sections of pavement that were at least 5 years old and carried current year traffic volumes greater than 15,000 vehicles per day. The study found that nearly 8 percent of all SRPM castings inspected were either missing or damaged. Approximately 35 percent of reflectors inspected were either missing or damaged. An analysis of risk factors showed that epoxy condition, total traffic since installation, and installation adequacy were the most significant factors in determining the condition of the marker casting and reflector. Total accumulated snowfall since installation, pavement type, pavement condition, and pavement age were also found potentially to play a role in SRPM failures. Total traffic since installation was found to offer the best ability to predict casting and reflector failure, and two models were developed to define potential SRPM inspection thresholds. The study recommends increased training for installers and inspectors and the development of a regular program for inspection of the marker casting and reflector. In addition, this study recommends that VDOT develop a SRPM installation protocol such that the raised markers are placed only in areas where they will be most effective.