An evaluation of retroflective signing materials under the 3-beam head-lamp system. Paper presented at the 54th Annual Meeting of the Transportation Research Board TRB, Washington, January 1975.

The purpose of the study described is to measure the comparative brightness of contemporary traffic signing materials under both the conventional 2-beam and the proposed 3-beam head-lamp systems. Because most traffic signs are retroflective, sign brightness is highly dependent on the illuminance supplied by headlamps. The high beam provides more light, and sign luminance under the proposed high beam is ± 2 times greater than it is under the current high beam. A discussion is added.