Daylight Saving Time and Trucker Fatigue


November 7, 2012

Maybe that hour ‘saved’ isn’t worth it

There’s a joke going around the internet as a quote attributed to an old Indian chief concerning his opinion of Daylight Saving time. It says, “Only the government would come up with a plan where it is believed that if you cut of the bottom of a blanket and then sew it to the top, you’d have a longer blanket.”

With that non-time addition in mind, is it possible Daylight Saving Time is a large contributor to truck driver fatigue?

Isaac Edery, Rutgers University professor of Molecular Biology and Biochemistry has been doing research on the circadian clock and the effects of losing that hour every March. Edery is a researcher at the Center for Advanced Biotechnology and Medicine, a joint venture of Rutgers and the University of Medicine and Dentistry of New Jersey.

In a recent article in the Asbury Park Press, Edery was quoted, “Studies indicate that when we transition to daylight-saving time in March, we lose 20 to 30 minutes of sleep each day just trying to adjust to the time change.”

Question: How does this loss of sleep affect truckers who have to deal with the transition both impacting their sleep habits and how they log the transition? According to Professor Edery “This loss can go on for days, weeks or even months. For some people, it can take quite a toll.” Is it possible this is true for many truckers?

It’s been estimated 1.9 million crashes a year, and one in six fatalities, involve a fatigued driver. The National Transportation Safety Board (NTSB) chairman Deborah A.P. Hersman has repeatedly said, “Tired drivers pose a safety risk because fatigue can degrade every aspect of human performance. Fatigue slows reaction time, impairs judgment and degrades memory.”

In an October 4, 2011, article for The Beverage Industry newsletter at, David Kolman, former trucker now trucking journalist, made the point: “The end of daylight saving time throws off our internal clocks. Studies find that it can take as long as two weeks for people to fully readjust their sleep schedule after the time change.”

Many studies support Kolman’s statement.

In April of 2004, an Australian study, “The Interaction Of Mild Obstructive Sleep Apnea, Sleep Deprivation, Circadian Factors and Alcohol In Driving Fatigue Risk,” prepared for NSW Motor Accidents Authority in Australia, refers to multiple studies spanning several decades about Daylight Saving Time and fatigue in relation to truckers. The report stated the following:

“Following on from an article published in the Journal Science in the 1970’s … showed that measurable changes in sleep pattern persist for up to five days after each time shift associated with Daylight Saving.” (Monk T., Folkard S. Adjusting to the changes to and from daylight saving time, Science, 1976). Stanley Coren, Ph.D., published a very interesting article in The New England Journal of Medicine titled Daylight Saving Time and Traffic Accidents. (New England Journal of Medicine, 1996); looking at the effects of daylight saving time zone changes on Canadian road accident rates.

Coren, using road accident data from the Canadian Ministry of Transport for 1991 and 1992 (approximately 20,000 reported accidents), showed that the spring shift to Daylight Saving Time, and the concomitant loss of one hour of sleep, resulted in an average increase in traffic accidents of approximately 8 percent, whereas the fall shift resulted in a decrease in accidents of approximately the same magnitude immediately after the time shift.

This suggested that even small changes in the amount of sleep people get can have major consequences in everyday activities, including the risk of traffic accidents. However, a similar recent study in Sweden did not show a measurable, immediate effect on crash incidence in Sweden associated with the shift to and from Daylight Saving Time. (Lambe M., Cummings P. The shift to and from Daylight Saving Time and motor vehicle crashes. Accident Analysis & Prevention 2000.).

In October of 1998, Alex Vincent, Ph.D., with Transport Canada, refuted Dr. Coren’s findings in a letter to The New England Journal of Medicine saying Dr. Coren’s hypothesis was flawed.

Dr. Vincent stated, “The results of a recent Canadian study call into question Coren’s findings that motor vehicle crashes increase by 8 percent following the change to Daylight Saving Time and decrease by 7 percent after the change to standard time. The study extended Coren’s analysis, using the same data source. First, data from the days between the Monday preceding the time change and the Monday one week afterward were analyzed. Second, Coren’s hypothesis was statistically tested with data from the years 1984 to 1993, to evaluate the significance of any differences obtained.

The mean motor vehicle crash rates for the Monday one week before the change to standard time were compared with those for the Monday immediately after the change and showed a significant increase. This result is inconsistent with Coren’s hypothesis. A paired t-test showed that the mean rate of 188.5 for the Monday immediately after the change was not significantly different from the mean rate of 186.5 for the Monday one week after the change.”

Dr. Coren responded, “In my study of the effects of Daylight Saving Time on traffic accidents, I found increased accident rates on the Monday after the spring shift in time and decreased rates in the fall. I interpreted this in terms of sleep time lost or gained. Vincent uses a larger data base than that available to me and fails to replicate these results. Unfortunately, Vincent’s analyses are based on t-tests of annual counts, rather than more sensitive, pooled relative-risk measures. More important, analysis of recent data from larger data banks gives me reason still to believe that the shift to Daylight Saving Time in the spring is associated with an increased risk of accidents, although the rebound reduction in accidents in the fall may be more problematic.”

“These data are consistent with the hypothesis that a small decrease in the duration of sleep can increase one’s susceptibility to accidents. Although work schedules accentuate the loss of sleep after the spring shift to Daylight Saving Time, the absence of a reduction in accidents in the fall may reflect the fact that many people do not take advantage of the hour gained to extend their sleep.”

In September of 2009, Christopher M. Barnes and David T. Wagner published “Changing to daylight saving time cuts into sleep and increases workplace injuries” in the Journal of Applied Psychology, Vol 94(5). Barnes and Wagner reported they examined the influence of time changes associated with Daylight Saving Time on sleep quantity and associated workplace injuries.

In Study 1, they used a National Institute for Occupational Safety and Health database of mining injuries for the years 1983–2006, and they found that in comparison with other days, on Mondays directly following the switch to Daylight Saving Time—in which 1 hour is lost—workers sustain more workplace injuries and injuries of greater severity.

In Study 2, Barnes and Wagner used a Bureau of Labor Statistics database of time use for the years 2003–2006. They found indirect evidence for the role of sleep in the Daylight Saving Time/injuries relationship. Data showed that on Mondays directly following the switch to Daylight Saving Time, workers sleep on average 40 minutes less than on other days. On Mondays directly following the switch back to Standard Time, in which 1 hour is gained, there are no significant differences in sleep, injury quantity, or injury severity.

In the Canarise Courier (Brooklyn, NY) March 18, 2010 newspaper, an article titled ‘Daylight Saving Time Could Mean More Drowsy Drivers,’ reported: “Commissioner David J. Swarts of the New York State Department of Motor Vehicles and Chair of the Governor’s Traffic Safety Committee (GTSC) used the occasion of the switch to Daylight Saving Time to remind motorists of the dangers of drowsy driving. Daylight Saving Time went into effect last Sunday. Swarts said, “Motorists should be aware of the warning signs of fatigue and how to avoid drowsy driving, particularly as we adjust to the loss of sleep that comes with the switch to Daylight Saving Tim.,”

Blogger Alan Bristol with Truck Driver News wrote in his March 11, 2011 post, (just preceding the ‘spring forward’ of clocks on March 14), “I don’t know about you but the last thing my circadian rhythm needs is this biannual cheap shot. By the way, have you ever thought how ludicrous the term “Time Change” is? I mean there are still 24 hours in a day, right? It’s not as if we are changing the rotational speed of the earth on its axis or anything.”

Fifteen years after Dr. Coren’s study was published in The New England Journal of Medicine, the American Automobile Association (AAA) made a statement in support of Dr. Corens’s findings. In a November 7, 2011, article in The Washington Post, ‘Seasonal time changes disrupt drivers’ body clocks, survey finds,’ John B. Townsend II of AAA was quoted, “Studies show that traffic accidents noticeably increase for a week following the time change in both the fall and the spring. Motorists have a tendency to misjudge the impact being tired has on their driving ability. That puts themselves and others at risk.”

It seems that with the preponderance of research and reports on Daylight Saving Time and the overwhelming evidence that it’s detrimental to one’s internal clock– causing fatigue–that the FMCSA or the National Highway Safety Administration would be taking a far more serious look at whether Daylight Saving Time should be repealed. After all, an 8% increase in vehicle crashes the week after the start of Daylight Savings Time is significant.

Timothy Brady © 2011 Contact Brady through
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