Citation

Nagel GA. Highw. Res. Board bull. 1957; 163: 17-20.

Copyright

(Copyright © 1957, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

The installation of a highway lighting test strip was made for the purpose of measuring by competent comparative observation, the relative effectiveness of the various types of highway lighting installed. In an attempt to evaluate visibility under the different types of lighting installed on the test strip, a sequence of pictures was taken for each type with the camera placed approximately 50 feet behind the luminaire for one sequence, and approximately 50 feet in front of the luminaire for the second sequence. After the first group of photographs had been taken, it was noted that there was a variation in pavement brightness background due to curves and grades in the roadway, so the photographs for the conventional mercury and fluorescent installations were taken in the north lane with the camera ahead of the luminaire, and in the south lane with the luminaire ahead of the camera. A variation is seen in the halation around the luminaires in the first pictures taken with short exposures in the respective sequences, and it is quite possible that this relationship could be a measure of the brightness of the luminaire. Obstacle recognition at a distance of about 500 feet takes place at approximately one-fifth-sec. Exposure in all of the picture sequences. The photographs indicate that obstacle recognition was about equal under all the luminaires, despite the fact that foot-candles and foot- lamberts varied considerably. On the basis of threshhold recognition, the study seems to bear out the claims of some vendors that visibility is better under linear-type of luminaires of low brightness, particularly with linear light sources such as the fluorescent lamp, which in this instrumentation showed the lowest foot-candle and foot- lambert readings. It is noted that in the sequences with the luminaire ahead of the camera, definite fogging of the film takes place after 1-sec, exposure under the 400-watt conventional mercury and the 400-watt linear mercury luminaires, after 2-sec. Exposure under the 250-watt linear mercury luminaire, and after 4-sec. Exposure under the 400- watt fluorescent luminaire. In contrast to this, the picture sequences with the camera ahead of the luminaire show fogging starting at 4-sec. Exposure 1nder the 400-watt conventional mercury, the 400-watt linear mercury, and the 400-watt fluorescent.