PARIS - A new study has found that drivers who use cruise control and speed limiters are prone to drowsiness when the road is empty and have significantly reduced reaction times when traffic gets busy.

Details of the study funded by the Vinci Autoroutes Foundation were released this week. It included 90 French drivers, divided into three age groups and put through a driving simulator for three days. All the drivers showed drowsiness and slowed reaction times using cruise control and speed limiters, but the youngest drivers -- ages 18 to 30 -- were most affected by fatigue, the study found.

Andre Dufour, the researcher with the University of Strasbourg who carried out the study, said cruise control and speed limiters help drivers obey the speed limit but should be used sensibly.