In this paper, the design and conduct of a controlled field experiment to measure the effect of five alternative reduced lighting techniques on individual driver detection of a simulated hazard on theroad surface of an urban freeway are discussed. The results of thisexperiment demonstrate significant decrements in drivers' ability to detect a 6-in.-High, semi-hemispherical, 18 percent reflective gray target under normal freeway traffic conditions as alternative reduced lighting tactics are implemented. In relation to a roadway fullylit by 200-w high-pressure sodium lamps at 68 to 88 ft, staggered spacings, and 30-ft mounting heights, test subjects could detect the simulated hazard only as the distance to the target was progressively shortened for the following conditions: uniformly dimmed at 75 percent power, uniformly dimmed at 50 percent power, every other luminaire extinguished, one side of roadway extinguished, and no lighting.Further, subjective ratings of target visibility under these test conditions were in general agreement with the detection response data. Pavement luminance and horizontal illumination were both strongly associated with the pattern of results in the controlled experiment, whereas calculated visibility index (v.I.) Values showed a slightlydiminished but still strong association with the behavioral data. This paper appeaed in transportation research record no. 1149, Visibility for highway guidance and hazard detection. For covering abstract see IRRD no 817811.
Samenvatting