Previous research has shown that caffeine and a <15-min nap effectivel
y and separately reduce sleepiness in drivers for 1 hr. In the present
study, we examined in 12 sleepy individuals the treatments combined,
taken during a 30-min break, prior to a longer (2 hr) continuous monot
onous afternoon drive in a car simulator. Nonnap comparisons were 200
mg caffeine only and placebo. For placebo, driving incidents, subjecti
ve and electroencephalographic measures of sleepiness all reflected a
mid-afternoon peak. This peak was significantly reduced by caffeine an
d eliminated by the combined treatment, which reduced incidents to 9%
of placebo levels versus 34% of placebo levels for caffeine alone. Nap
s comprising ''nonsleep dozing'' were still effective.