Sleepiness, Alcohol and Traffic Safety

Alcohol and sleepiness are leading causes of serious motor vehicle accidents worldwide. Alcohol and sleepiness may also interact to cause greater driving performance decrements and accident risk, particularly when behaviourally or pathologically induced (e.g. restricted/fragmented sleep) and times of normally increased sleepiness (i.e. early morning and mid-afternoon) coincide. Patients with sleep disorders such as obstructive sleep apnoea and possibly some others appear to be especially vulnerable to the effects of moderate sleep loss as well as low doses of alcohol on driving performance. The interactive effects of alcohol and sleepiness may be partly explained through their actions on the sleep/wake promoting brain regions and the pre-frontal cortex responsible for higher order cognitive function. This chapter presents evidence from both epidemiological and experimental research on the effects of alcohol, sleepiness and their combination on driving performance and accident risk. The evidence warrants further attention and awareness of interactions between alcohol and sleepiness, as both factors are likely to often co-exist in the lead up to a motor vehicle accident. Current BAC laws, particularly for young drivers who are most at risk, warrant further review and potentially revision.