In its report, Drowsy Driving and Automobile Crashes, National Highway Traffic Safety Administration, NCSDR/NHTSA Expert Panel on Driver Fatigue and Sleepiness, the National Highway Traffic Safety Administration (NHTSA) conservatively estimated that 100,000 police-reported crashes were the direct result of driver fatigue each year, resulting in an estimated 1,500 deaths, 71,000 injuries, and $ 12.5 billion in monetary losses.
The NHTSA reported that studies found people’s cognitive-psychomotor abilities to be as impaired after 24 hours without sleep as with a blood alcohol content of 0.10%, which is higher than the legal limit for a driving while intoxicated (DWI) conviction in all states. Although sleepiness and alcohol are distinct crash causes, the data also showed some evidence of overlap; NHTSA found that drivers had consumed some alcohol in nearly 20 percent of all sleepiness-related, single-vehicle crashes. Many researchers have shown that sleepiness and alcohol interact, with sleep restriction exacerbating the sedating effects of alcohol, and the combination adversely affecting psychomotor skills to an extent greater than that of sleepiness or alcohol alone.
The differences between being impaired by a lack of sleep or due to a sleep disorder and being impaired by alcohol consumption can be important when a motorist is charged with DWI drunk driving. Unfortunately, the behaviors and appearances associated with lack of sleep and intoxication often coincide, such as lane weaving, bloodshot eyes, and slurred speech. If these characteristics are associated with the odor of alcohol on the breath, it is likely that the law enforcement officer will arrest the motorist for DUI.
If a motorist is chronically sleepy, is involved in sleep-restrictive work patterns (shift-work), or suffers from untreated sleep disorders such as sleep apnea syndrome or narcolepsy, such impairment may be available as a defense to a criminal charge of driving while intoxicated. However, it becomes a matter of proof. If there are no breath tests results due to refusal, there was no real proof that the impairment was not alcohol related.