The correct answer to this open question is the following.
The question is incomplete. Indeed, if the question is just "Is lack of sleep causing traffic fatalities?" The answer would be "yes."
If the question is to complete the statement, then it would be the following:
A study conducted under the auspices of the National Highway Traffic Safety Administration found that the average number of fatal crashes caused by drowsy drivers was approximately 1550.
Commonly, drivers feel drowsy when driving, especially the ones that take the highway for long hours of driving. That is why you must constantly make stops to take a rest. This is a preventive measure that could save lives.