Behavior like this may be characteristic of motorists who have a strange and uncontrollable form of sleepiness called narcolepsy. Their main symptom is an imperative and sudden need to take short, frequent naps at any time and in any place, including the highway. Narcolepsy itself is not fatal, has no discernible cause, and can be readily treated, if not cured, with drugs. A recent issue of Family Safety, a National Safety Council publication, suggests that untreated cases of narcolepsy are a factor in at least some of the so-called "mystery crashes" in the U.S. which have to apparent cause. The American Medical Association estimates that