Simulated driving performance and peripheral detection at mesopic and low photopic light levels

This paper describes research conducted to measure people' ability to perform a simulated driving task and respond to peripheral targets at mesopic and low photopic light levels under different spectral power distributions (SPDS). A computer-controlled driving simulator apparatus was employed. An achromatic projected driving scene could be controlled in terms of luminance and SPD using filters. Subjects drove simulated roadway courses; their average speed, frequency of crashing and subjective ratings of brightness were measured. As expected, driving performance and subjective ratings improved with photopic luminance. SPD had no measurable an driving performance or brightness ratings. Subsequent tests shawed, however, that the detection of targets located in the peripheral visual field (positioned where potential visual hazards to a driver might be located) was highly dependent on both luminance and SID. Rods and cones both appear to contribute to peripheral target detection even at luminances traditionally considered to be strictly photopic. The results and their implications are discussed in the context of previous research.