Drowsy driving is known to be a problem. Official federal crash statistics estimate that about 2.5 percent of all fatal car accidents involve a drowsy driver. But those estimates are not considered very accurate, as determining if a driver was sleepy before a crash is difficult.

In fatal crashes, the driver cannot answer any questions concerning his or her condition prior to the crash, and for drivers who survive a motor vehicle accident, they may not realize they were drowsy or may be to reticent to admit to a police officer that they fell asleep at the wheel.