The current UK legal blood alcohol concentration (BAC) limit of driving is 0.08% and police roadside breathalysers do not detect BACs below 0.07%. This study assesses whether BACs below half the UK legal limit and therfore undetectable, cause performance decrements in alert drivers and further impair performance in already sleepy drivers. Twelve young men underwent a trial with alcohol vs placebo and normal sleep vs sleep restriction treatments. Each participant drove in an interactive car simulator form 14.00-16.00h in a dull monotonous dual carriageway. During the drive lane drifiting, subjective sleepiness and objective sleepiness (EEG-electroencephalogram) were measured. Both alcohol and sleep restriction alone produced a similar significant deterioration in all measurements. Combining the two treatments further exacerbated lane drifiting, mirrored by an increase in objective sleepiness. However these changes were not reflected in subjective sleepiness. In already sleepy drivers, there was an apparent lack of realisation that alcohol had further increase their sleepiness and caused their driving performance to deteriorate.
Abstract