Sleep Deprivation and Time Awake Decreases Driving Performance - A key to off-the-job injury prevention which applies on the Job as well

BrooklynDodger believes that extended work hours cause traffic accidents. A worksite-based off-the-job injury program must address this. Time since waking is probably the best measure of increased risk. Prior sleep deprivation increases risk when added to time since waking.

These findings are more important than driving - they probe the effect of work hours on all types of errors, including both those which cause injury and those which cause production and quality problems.

In this study, the sleep restricted drivers arrived in the lab at 9 pm, had 2 hours sleep, and started driving 8 hours after waking, continuing to drive until 18 hours. The unrestricted drivers started driving 1 ½ hours after waking and continued to drive until 11 ½ hours after waking. From the first cycle, the sleep restricted drivers were driving poorly. Rested drivers also showed decreased performance later in the driving cycle.

The investigators concluded “Our findings show that duration of driving is not the main factor to explain driving impairment and that time awake and previous sleep duration have a much bigger impact. Professional regulations and work schedules should integrate sleep schedules before and during the work period as an essential dimension for safe driving.”


Decline in Driving Performance over a 10 hour period

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Edited abstract and summary:

Healthy young males drove 625 miles with a co-pilot over 10 h during five 105 min sessions on an open [French] highway. In the sleep restriction condition, subjects were allowed to sleep only from 23:00 to 01:00. All drivers started driving at 9 am and drove 5 sessions with breaks ending at 7 pm. Subjects were instructed to maintain a constant speed (130 kph or 80 mph) and not to cross the painted lines separating the lanes except to pass a slower vehicle. Self-rated fatigue and sleepiness were recorded before each session, number of inappropriate line crossings from video recordings and simple reaction time (RT) were measured.

In the rested condition, co-pilots never interfered with driving. In the sleep-restricted condition, co-pilots interfered 61 times with the driving of subjects and several had to stop because of fatigue. No subjects had to stop driving during the rested condition. Line crossings increased during the day for both rested and restricted subjects.

Line crossings increased 8-fold with sleep restriction (535 crossings in the sleep-restricted condition versus 66 after non-restricted sleep). Crossings increased with increasing sleepiness score during the next driving session in the sleep-restricted. Rested subjects drove 1000 km with four shorts breaks with a minor performance decrease [Minor is in the eye of the other drivers, this was still an effect]. Sleep restriction induced important performance degradation even though time awake (8 h) and session driving times (105 min) were relatively short. Performance degradation was associated with sleepiness and not fatigue. Sleepiness combined with fatigue significantly slowed reaction time.

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Accident Analysis & Prevention Volume 37, Issue 3 , May 2005, Pages 473-478

Fatigue, sleep restriction and driving performance

Pierre Philipa, , , Patricia Sagaspeb, Nicholas Moorec, Jacques Taillarda, André Charlesb, Christian Guilleminaultd and Bernard Bioulaca aClinique du Sommeil, CHU Pellegrin, Place Amelie Raba Leon, 33076 Bordeaux Cedex, FrancebLaboratoire de Psychologie, EA 3662, Université Bordeaux II, 33076 Bordeaux Cedex, FrancecDépartement de Pharmacologie, Université Bordeaux II, 33076 Bordeaux Cedex, FrancedSleep Research Center, Stanford Medical School, Stanford, CA, USA