After analyzing the results, they found an estimated 7 percent of all motor vehicle crashes in America and 16 percent of fatal crashes involve driver drowsiness.
Upon further investigation, they discovered drivers who got fewer than four hours of sleep were 15 times more likely to cause a car collision, compared to those who received seven to nine hours. In fact, they compared the risk to that of drivers with a blood alcohol concentration roughly 1.5 times the legal limit.
"Being awake isn't the same as being alert. Falling asleep isn't the only risk," co-author Brian Tefft said in a statement. "Even if they manage to stay awake, sleep-deprived drivers are still at increased risk of making mistakes—like failing to notice something important, or misjudging a gap in traffic—which can have tragic consequences."
The scientists also revealed drivers who slept less than four hours had an elevated risk of single-vehicle crashes, which are more likely to result in injury or death. Furthermore, those who had changed their sleep or work schedule in the past week and those who had been on the road for three hours or longer without taking a break also had an increased risk.
Want to learn more about the findings? Take a look at the full report here.