Drivers' visual scanning impairment under the influences of alcohol and distraction: a literature review.

Alcohol intoxication and distraction are two of the leading factors associated with impaired driving and fatalities, especially among younger drivers. However, it is currently unclear how these conditions affect mechanisms of visual attention considered essential for driving. The present article first reviews the literature to provide an overview of visual attention as it relates to driving. Secondly, the effects of alcohol and distraction on neurocognitive mechanisms of visual attention are summarised to provide a background which informs discussion of selected driving studies. Visual scanning impairment is identified as a consequence of both alcohol and distraction. Thus, experimental studies combining the use of simulated driving and eye tracking technologies are selected and critically reviewed to assess the relationship between eye movements and driving errors as possible indicators of visual scanning impairment. Seven of the eight studies selected investigated the effects of distraction while only one addressed alcohol. Evaluation of these studies suggests that distraction may affect visual scanning by increasing cognitive load which interferes with visual processing. The evidence for effects of alcohol on drivers' visual scanning capacity is currently scarce due to the lack of research with a specific focus on impairments of eye movement in intoxicated drivers. Lack of consistency between studies is identified as a current issue which makes it difficult to compare the results of different studies. Finally, we note that our strict selection of driving studies to avoid greater disparity between them is a limitation of the present review.