Experts from CNRS, Inrets, the University of Bordeaux and the University of Stockholm say that their study was able to determine whether 2, 4 and 8 hours of nocturnal driving affected driving performance differently.
Lead researcher Pierre Philip, from the Laboratory for motion, adaptation and cognition (CNRS/Université Bordeaux 1 and Bordeaux 2), has revealed that with a view to evaluating the fatigue caused by accumulated driving time, the team made 14 young volunteers drive on an open highway during three nocturnal driving sessions: from 3-5 am, 1-5 am and 9 pm-5 am.
While driving durations were different, sleep pressure at the end of the driving session was identical because of the late hours, reports the Science Daily.
The researchers calculated the number of times the drivers veered off course, and crossed the lateral lines inappropriately during the last hour of driving in each session.
They said that compared with the reference session (9-10 pm), the risk of inappropriate line crossing was six times greater during the 3-5am driving session, 15 times greater during the 1-5am driving session, and 24 times greater during the 9 pm-5am driving session.
The team also observed that compared with the shortest driving session (3-5 am), the risk of inappropriate crossing of the lateral lines increased 2.6 times during the 1-5 am driving session, and was fourfold during the 9 pm-5 am driving session.
Based on their observations, the researchers came to the conclusion that extended nocturnal driving does have a very large impact on driving performance.
They insist that their findings raise the question of whether maximum durations for driving at night should be reconsidered.