From Longman Dictionary of Contemporary Englishfall asleepfall asleepa) SLEEPto begin to sleep Grandad fell asleep watching TV. One in seven road accidents is caused by drivers falling asleep at the wheel (=falling asleep while driving). b) DIE literary used to mean that someone dies, when you want to avoid saying this directly → asleep
Examples from the Corpus
falling asleep at the wheel• One in seven road accidents is caused by drivers falling asleep at the wheel. 