An assessment of indirect factors affecting reflective sign brightness. Paper prepared for the 55th Annual Meeting of the Transportation Research Board TRB, Washington, D.C., January 1976.

The study was undertaken to determine the effect of stream traffic and road surface conditions on the brightness of retro-reflective signing materials used for guide, warning and regulatory signs. Field luminance measurements were made of a variety of retro-reflective materials with vehicle configurations simulating various stream traffic densities. Several stream traffic spacing patterns were developed to represent various traffic volumes.