A new study commissioned by the European Commission and the International Road Transport Union claims that of 624 truck crashes studied, only 6% involved driver fatigue.

When fatigue was identified as the cause of the accident, the European Truck Accident Causation report said “Most accidents happen between [2 and 2:59 a.m.], probably the time when the driver’s biorhythm is at a low point, and from [3 and 3:59 p.m.] when it is nearly the end of the working day.”

The report also said fatigue “plays only a minor role” in accidents in cities. It did note that of the accidents where fatigue played a role, 37% of those were fatal and 68% involved another vehicle.

Overall, the report found that human error was responsible for 85.2% of all accidents, although only 25% of those can be attributed to the truck driver. Weather (4.4%), infrastructure (5.1%) or technical failures of the vehicle (5.3%) were the other main factors in crashes.

The report broke down the accidents into five main categories: accident at intersection, accident in queue (an incident when all vehicles are traveling in the same direction), accident due to lane departure, accident during an overtaking maneuver, and single truck accidents.

More than 30% of the time, the cause of accidents at an intersection are due to failure to observe intersection rules or non-adapted speed for the situation. Speed, insufficient distance or inattention are the cause of more than 50% of incidents of vehicles in a queue.

Speed is also the main cause of incidents when lane departure was cited as the cause. Nearly 20% of incidents when trucks are the cause involved speed. When the truck is the cause of an accident in an overtaking maneuver, an improper lane change is the reason 15.7% of the time, but fatigue came in second, at 8.8%.

Speed remains the top cause in single-truck accidents as well, causing 20.3% of incidents. Fatigue is the reason18.9% of the time.

Still the report said that fatigue, only plays a minor role in accidents, and most of those occur on highways.

“Regarding the place of accidents where fatigue is the main cause, nearly 90% happen on highways or on inter-urban roads,” the report said. “Fatigue as an accident cause plays only a minor role in cities.”

The report made a number of recommendations, including the use of adaptive cruise control, traction and stability control systems, active roll stabilization systems, and improved signage on roadways. It also suggests several measures carriers can take, including helping drivers do a better job of planning their trips around infrastructure and road restrictions, and better training of drivers to maintain proper speed as well as learning to anticipate the actions of other vehicles.