The actual and estimated ability of younger and older drivers to see and steer in challenging visual conditions: A test of the selective degradation hypothesis.

摘要

Research has shown that, at night, drivers are comfortable overdriving their headlights. The selective degradation hypothesis suggests that, in darkness, drivers are unaware that selective visual functions such as acuity diminish, reassured by the fact that their steering abilities are preserved (Leibowitz & Owens, 1977). Previous researchers have presented evidence to support this hypothesis by confirming that the ability to steer---but not the ability to see details---is preserved at night (e.g. Owens, 2003; Owens & Tyrrell, 1999). However, no empirical investigations have directly explored the extent to which drivers are aware of how luminance affects either visual guidance (steering) or visual recognition (acuity). Luminance effects were tested by asking 36 visually healthy licensed drivers from three different age groups (18-21, 35-50, and 65-78 years) to drive a fixed-base driving simulator at a moderately high speed on continuously curvy roads in a broad range of luminance conditions (-3 to 1 log cd/m2). Before driving, participants estimated their performance for both steering and acuity using a new psychophysically based method that allows direct comparisons. Overall, participants correctly estimated that their acuity would decline as luminance decreased but were unaware that their steering capabilities would not. The older drivers overestimated their acuity while both university students and middle-age adults underestimated their acuity. None appeared to appreciate that acuity and steering are supported by separate visual mechanisms. This research has implications for drivers, pedestrians, and roadway designers, whose knowledge of selective degradation could result in increased nighttime safety.