ABSTRACT
One of the leading causes of motorcycle crashes are right-of-way violations in which another road user, typically a car driver, turns across the path of an oncoming motorcycle (Clarke et al., 2007). Before discussing psychological theories that could explain the human factors underlying this crash type, it is instructive to consider a basic behavioural taxonomy and failure classification of the typical errors involved in car-motorcycle crashes. Crundall, Humphrey and Clarke (2008) proposed three key behaviours that drivers must execute in order to avoid collisions: first, they must look at the motorcycle; second, they must detect its presence; and finally, they must appraise it appropriately. Detection errors arise from failure of one of the first two stages, and comprise the majority of crashes and involve other road users failing to detect the motorcycle or detecting it too late to avoid a collision (Pai, 2011). Such crashes are referred to as ‘look but fail to see’ crashes because afterwards drivers often indicate that they looked at the rider’s location but failed to detect the motorcycle. In contrast, decision errors arise from inappropriate appraisal; these errors occur when another road user detects a motorcycle but misjudges its speed and/or location and consequently accepts a gap that is too small (Pai, 2011). Both detection and decision errors frequently occur in conditions of good visibility, when drivers presumably have the best possible chance to detect and appraise an oncoming vehicle. Aggregated crash data indicates that the ‘modal’ motorcycle crash occurs during the day in urban areas, good weather conditions and involves an experienced driver failing to see a motorcycle and consequently turning across the rider’s path (Hancock et al., 2005). This suggests drivers’ difficulties in perceiving and accurately appraising motorcycles result at least partially from cognitive factors; if they were purely perceptual limitations then they would be most common under conditions of poor visibility.
