Washington, June 11 : A new research has suggested that extended driving impairs an individual's driving performance at night, and should, therefore, be limited.
For the study, researchers at Universite Bordeaux in France focused on 14 healthy young men.
The participants drove in three nocturnal driving sessions (3-5 a.m., 1-5 a.m. and 9 p.m.-5 a.m.) on an open highway.
Inappropriate line crossings in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were analyzed.
Researchers found that as compared to the 3-5 a.m. driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 in the 1-5 a.m. driving session and by 4.0 in the 9 p.m.-5 a.m. driving session.
Compared to the reference session (9-10 p.m.), the incidence rate ratio of inappropriate line crossings were 6.0 in the 3-5 a.m. driving session, 15.4 in the 1-5 a.m. driving session and 24.3 in the 9 p.m.-5 a.m. driving session.
The study showed that self-related fatigue and sleepiness scores were both correlated to driving impairment in the 1-5 a.m. and 9 p.m.-5 a.m. driving sessions and increased significantly during the nocturnal driving sessions compared to the reference session.
"Up to now, regulations have taken into account maximal duration of driving, but the cumulative effects of sleepiness and fatigue were never studied or integrated in the driving regulation," said Pierre Philip, of Universite Bordeaux in France, one of the authors of the study.
"Here, we show that performance is badly affected by time of the day, and therefore, we think that a warning to limit maximum nocturnal driving duration should be included in professional safety recommendations," Philip added.
It is recommended that adults get between seven and eight hours of nightly sleep.
The study has been presented at SLEEP 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies (APSS).