Citation

Breckenridge FC. Highw. Res. Board bull. 1954; 89: 68-69.

Copyright

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

DOI

unavailable

PMID

unavailable

Abstract

The utilization of light in fog is principally governed by two basic principles: (1) the attenuation of the light exponentially with the distance it travels, and (2) the visibility of lights and objects depends generally on the contrast between their brightness and the brightness of their background, the threshold for the necessary contrast being approximately a constant ratio to the background brightness. These principles give signal lighting an advantage over illumination as a means of controlling traffic fog. Highway lighting suffers from the disadvantage of losing some of its intensity in reflection at the object seen and from the dazzling effects of the lights themselves. Aviation lighting research developed three devices which may be useful in connection with solving the highway traffic problem: (1) the fog simulator, which so controls the intensities of lights that the pilot or driver constantly sees only a few lights ahead of him even when operating in clear weather, (2) the kinorama, which simulates the visual appearance of lights as seen by a pilot during the landing operation, the apparent location of the lights corresponding to the manipulation of controls simulating those of an airplane and (3) the transmissometer, which measures the transmission of light through the atmosphere and gives an indication of the density of fog at a desired location, which may be remote from the measuring instrument. A new system having a continuously moving signal configuration is suggested.