This paper describes research conducted to measure people's ability to perform a simulated driving task and respond to peripheral targets at mesopic and low photopic light levels under di~~~t spectral power distributions ~s~~). 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.
Reducing the potential for crashes involving front line service workers and passing vehicles is important for increasing worker safety in work zones and similar locations. Flashing yellow warning beacons are often used to protect, delineate, and provide visual information to drivers within and approaching work zones. A nighttime field study using simulated workers, with and without reflective vests, present outside trucks was conducted to evaluate the effects of different warning beacon intensities and flash frequencies. Interactions between intensity and flash frequency were also analyzed. This study determined that intensitiesof 25/2.5 cd and 150/15 cd (peak/trough intensity) provided the farthest detection distances of the simulated worker. Mean detection distances in response to a flash frequency of 1 Hz were not statistically different from those in response to 4 Hz flashing. Simulated workers wearing reflective vests were seen the farthest distances away from the trucks for all combinations of intensity and flash frequency.
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