How to recognize a fatigue-related crash?
Unlike the situation with alcohol-related crashes, no blood, breath, or other measurable test is currently available to quantify levels of sleepiness at a crash site. Thus current understanding of typical crash related characteristics come largely from inferential evidence.
In the United Kingdom, fatigue related crashes have been identified using the following criteria:
- The vehicle has run off the road and/or collided with another vehicle or object
- There is an absence of skid marks or braking
- The driver could see the point of run-off or the object hit prior to the crash
- Other causes are eliminated e.g. mechanical defect, speeding, excess alcohol, bad weather; and
- Witnesses may report lane drifting prior to the crash 
Similarly in the United States, the Expert Panel on Driver Fatigue and Sleepiness  characterises a fatigue-related crash as follows:
- The problem occurs during late night/ early morning or mid-afternoon
- The crash is likely to be serious
- A single vehicle leaves the roadway
- The crash occurs on a high-speed road
- The driver does not attempt to avoid a crash
- The driver is alone in the vehicle