According to the British Royal Society for the Prevention of Accidents, driverfatigue contributes up to 20% of road accidents and up to a quarter of fatal and serious accidents.
Blankets and pillows found in the wrecked van indicate the group may have been traveling all night, possible evidence that driverfatigue may have played a role in the collision, Montijo said.
The National Transportation Safety Board said in July that driverfatigue and other factors likely caused the crash, finding Cheung had limited opportunities for quality sleep in the days before the accident.