When people do not get enough sleep, their judgement and abilities maybe impaired. That means they should avoid doing tasks that require great alertness, such as driving a car. If a person falls asleep or holding a steering wheel of their car. There could be a terrible accident. To be asleep at the wheel creates danger not only for the driver and any passengers, but also for anyone else on the road.

 

As an idiom, we use this phrase to indicate about someone who's not alert enough when something critical is taking place or not paying for attention to any important situation. If a person fails to respond in a proper manner at a precarious movement, we say they were asleep at the wheel.