Author: H. L. Woltman and W. P. Youngblood, 3M Company

Sponsoring Agency:  Committee on Visibility

Date of Publication:  1975

Abstract:

The purpose of the study described in this paper 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 retroreflective, sign brightness is highly de-pendent on the illuminance supplied by head lamps. A systematic evaluation performed by the authors led to a general understanding of sign luminances for conventional 2-beam performance for Interstate Highway System signs. The design experiment was developed to evaluate the relative change in sign luminance should the 3-beam system be standardized. Photometrically selected 2- and 3-beam head-lamp sets were obtained from 2 lamp manufacturers, installed in standard-size passenger cars, and aligned. Night luminance measurements were made of retroreflective sign materials by using a telephotometer installed at driver eye position. Luminance measurements were taken at 7 distances from the traveled lane on a uniformly graded tangent section of test road. The proposed low beam is not different from the current low beam. The sign luminance under the proposed mid beam is approximately 4 times greater than it is under the low beam. The high beam provides substantially more light, and sign luminance under the proposed high beam is approximately 2 times greater than it is under the current high beam.

No. of Pages:  14