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Mark Gould, John Wann, Damian Poulter, Shaun Helman; Judging the approach speed of motorcycles and cars in night-time driving conditions. Journal of Vision 2011;11(11):931. doi: 10.1167/11.11.931.
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The ability to accurately judge the approach speed of a motorcycle is critical in order to avoid right of way violation accidents at junctions. Research has demonstrated that individuals consistently judge the time to contact (ttc) of a motorcycle to be later than that of a car (Horswill, Helman, Ardiles, & Wann, 2005). However, the majority of studies surrounding the judgement of motorcycle speed have taken place in daylight hours and very little is known about how individuals make these judgements in night-time conditions; where the perceptual information available is severely reduced. We measured the accuracy of adult drivers' speed judgements for motorcycles and cars in night-time conditions. Solid white headlights were presented on a black background in a virtual environment and arranged to represent a motorcycle or car headlight formation, both with the same headlight diameter. These stimuli were presented either simultaneously or sequentially with a fixed ttc of 4 seconds at their closest position (sufficient time to pull out of a junction). Participants were asked to make a 2FC judgement as to which vehicle was travelling the fastest and thresholds for speed differences were estimated using an adaptive (best-PEST) psychophysical procedure. Results demonstrated that individuals were significantly more accurate when judging the speed of the car compared to motorcycle, which suggests that they are using the separation of the headlight stimuli to make judgements rather than the looming of the headlight contours. The difference between car and motorcycle stimuli can then be offset to some degree by re-arranging the motorcycle lighting configuration. The results indicate that people misjudge the approach speed of motorcycles in night-time conditions; thus increasing the likelihood of a driver pulling out in front of them and causing an accident. Engineering modifications that could reduce this risk are currently being investigated. Research supported by the UK EPSRC and UK ESRC.
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