Inlaid Pavement Marker Evaluation

The objectives of this study were to assess inlaid pavement marker (IPM) performance and estimate their safety effectiveness. IPM performance was evaluated through a count of marker presence and a feedback survey from participants who viewed dry and wet night videos of IPM sections in the St Louis area. The safety effectiveness of IPMs was evaluated using a rigorous state-of-the-art empirical Bayes (EB) before-after crash analysis. The marker presence assessment, unfortunately, didn’t provide any conclusive trends in IPM performance. Newer IPM sections had higher percentages of missing markers than older sections, and there were too many unknown variables to determine the source of the unexpected differences. The unanimous conclusion of the nighttime video visibility survey was that drivers and passengers traveling on a wet night feel that IPMs are very important to the visibility of the roadway’s lane lines. For the EB analysis, installation and reference site data were used to examine the effects for specific crash types, including total, fatal and injury, wet pavement, nighttime, nighttime wet pavement, lane departure, wet pavement lane departure, nighttime lane departure, and fatal and injury lane departure. Based on the aggregate results, IPMs, when installed with pavement resurfacing, significantly reduce all crash types examined.  The report is available from Missouri Department of Transportation's web site at https://spexternal.modot.mo.gov/sites/cm/CORDT/cmr20-009.pdf