Retroreflective Raised Pavement Marker Field Testing: Results of the First Year Evaluation (1946-2)

This report documents the results of field testing of seventeen types of retroreflective raised pavement markers (RRPMs) installed in August 1992 at four interstate locations around San Antonio, Texas. Reflectivity measurements were taken periodically at each site using a portable reflectometer. These data were supplemented with laboratory reflectivity measurements from RRPMs taken from each site and sent to the TxDOT testing laboratory in Austin, Texas.|Study results indicate that most of the RRPMs experienced significant losses in reflectivity over very short periods of time. Under the range of traffic conditions examined, many RRPMs dropped below approximate minimum reflectivity thresholds after six months in the field. Initial losses in reflectivity were due primarily to dirt accumulation on the reflective lenses. Over time, abrasions and weathering caused reflectivity losses to become permanent.|Three RRPM types that had thin glass layers epoxied over the reflective lenses were still providing significant levels of reflectivity after 54 weeks in the field at all of the test locations. For the other RRPMs, differences in reflectivity loss rates appeared to depend mostly upon the total traffic volumes passing next to the RRPMs at each test site, and less so upon the amount of truck traffic or lane-changing activity.