Citation

Janoff MS. Transp. Res. Rec. 1977; 628: 37-43.

Copyright

(Copyright © 1977, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

An experimental lighting system in an underpass on I-76 in Philadelphia was evaluated. The lighting system was designed to provide five levels of illumination ranging from 5382 lx (500 ftc) horizontal to 22 lx (2 ftc) horizontal. Low-pressure sodium-vapor lamps were used. The internal level was automatically set by a series of photocells external to the underpass and provided a ratio of internal to external illuminance of approximately 10 percent. Four measures were used to determine the effect of the improved illumination on traffic operations. These were (a) the effect on the number of traffic accidents, (b) the effect on vehicle-velocity maintenance (c) the effect on deceleration (braking) characteristics, and (d) the effect on subjective response of drivers to the new lighting. The photometric characteristics of the new lighting were evaluated and the Illuminating Engineering Society and the American Association of State Highway and Transportation Officials tunnel-lighting recommendations were compared. The results indicated that (a) the new lighting caused decreases in the velocity variability and in brake applications at the portal, (b) in general, as the internal lighting level increased, both the velocity variability and the number of brake applications decreased, indicating safer and smoother traffic operations, (c) drivers responded positively when the internal lighting levels were increased and there were no noticeable adverse effects caused by the low-pressure sodium-vapor lamps, (d) the Illuminating Engineering Society recommendations for tunnel lighting appear to be preferable to those of the American Association of State Highway and Transportation Officials, and (e) there was a reduction in the number of accidents inside the underpass and at the portal in the 6 months after installation of the new lighting.