Citation

Sherman WF. Highw. Res. Board bull. 1956; 127: 19-22.

Copyright

(Copyright © 1956, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

RESULTS are reported of an engineering and development program aimed at improving the sealed-beam headlamp for automobiles. Because of heavy highway traffic, night-driving conditions create a need of driving with the lower beam. This results in the need for an improvement in the lower beam pattern which would satisfy headlight requirements through a wider range of driving situations. A considerable increase in light intensity directed at the right hand side of the vehicle path was needed during the times the vehicle is operated with the lamps on the lower beams. Eleven different lamp designs, representing a planned effort at modifying lamp characteristics, were developed and submitted by the various lamp manufacturers. A filament cap was developed for mounting above the lower beam filament to reduce the stray light projected upward from the filament. This produced benefits for the driver in adverse weather situations. An increase in light at the source was accomplished by raising the wattage of each filament by five watts. Part of the modification of the lamp specification is accomplished by a change in the aim specification so the geometric center of the zone of highest intensity of the upper beam falls 0.4 degree below the photometer axis, as contrasted with the previous requirement of 0.6 degree. The value is emphasized of having headlamps aimed properly, both from the view point of getting better seeing distance at night and from the viewpoint of affording other drivers necessary glare relief.