Photometric Evaluation of Steady-Burn Warning Lights in Work Zones

This report documents the efforts and results of several photometric evaluations performed by researchers at the Texas A&M Transportation Institute to assess the performance of steady-burn warning lights in temporary traffic control devices used to delineate the correct travel path in work zones. The research included an assessment of the potential incremental increase in luminance (and benefit of that increase to drivers) during vulnerable driving conditions. These conditions included periods of heavy fog, periods when dirt and grime had accumulated on the channelizing device, and misalignment of warning lights. The researchers found that fog adversely affected the apparent luminance (and thus the visibility distance) of both retroreflective sheeting and warning lights. However, retroreflective sheeting was still likely to be visible at distances needed for purposes of path guidance and delineation, and the use of warning lights was unlikely to provide much additional value to motorists. The researchers also found that the accumulation of dirt and grime on the retroreflective sheeting of drums in Florida work zones did have an impact on device luminance. Although the use of warning lights did increase the overall luminance of channelizing drums, a greater increase in luminance was noted when the drums were clean. Finally, misalignment of lights significantly reduced their photometric value.