TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 92, Pavement Marking Materials and Markers: Real-World Relationship Between Retroreflectivity and Safety Over Time examines the safety effect of retroreflectivity of longitudinal pavement markings and markers over time on non-intersection locations during non-daylight conditions. A summry of this report is available as NCHRP Research Results Digest 305: Pavement Marking Materials and Markers: Testing the Relationship Between Retroreflectivity and Safety.