Citation

Davis EP, Fitzpatrick JT. Highw. Res. Board bull. 1954; 89: 7-15.

Copyright

(Copyright © 1954, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

At the present time, it is common practice to erect highway traffic signs low and close to the road. Four feet above and 8 feet out from the edge of the pavement seems to be the most-common position. This has been considered necessary to keep the signs nearer the hot spot of the headlight beams. But, it puts the signs in a poor spot from a dirt accumulation point of view. Extensive tests on the rate of dirt accumulation have been run on test signs over a 19-month period. Splash and spray areas of highways were evaluated.

RESULTS indicated there is a sharp reduction of dirt accumulation at 6 feet above and 8 feet out from the edge of the pavement. Moving signs 2 feet out and 2 feet up from the conventional position reduces dirt accumulation to about a third. This is enough so that rains tend to keep the signs clear and reduce the need for maintenance. The reduction in headlight intensity, because the signs are further from the hot spot, is more than made up for by selecting more-efficient reflecting materials. In addition to having cleaner and more effective signs on the highway, the maintenance engineer is helped because it is easier to plow, mow, and blade highway shoulders with sign posts 2 feet farther out from the edge of the pavement.