COUNTERACTING DRIVER SLEEPINESS - EFFECTS OF NAPPING, CAFFEINE, AND PLACEBO

Sleepy drivers should ''take a break,'' but the efficacy of feasible a dditional countermeasures that can be used during the break is unknown . We examined a shorter than 15 min nap, 150 mg of caffeine in coffee, and a coffee placebo, each given randomly across test sessions to 10 sleepy subjects during a 30-min rest period between two 1-hr monotonou s early afternoon drives in a car simulator. Caffeine and nap signific antly reduced driving impairments, subjective sleepiness, and electroe ncephalographic (EEG)activity indicating drowsiness. Blink rate was un affected. Sleep during naps varied, whereas caffeine produced more con sistent effects. Subjects acknowledged sleepiness when the EEG indicat ed drowsiness, and driving impairments were preceded by self-knowledge of sleepiness. Taking just a break proved ineffective.