Transportation Accidents

Diminished performance is not the only problem caused by being out of phase with one's environment. Worker and public safety also can be compromised. Although other factors may have been involved, fatigue should not be ruled out as a contributor to the following much publicized disasters:
                   Chernobyl                   1:23 AM
                   Bhopal                     12:40 AM
                   Three-Mile Island           4:00 AM
According to the National Safety Council, the average number of passenger deaths and the average rate of deaths (deaths per 100 million passenger miles) between 1982 and 1992 for each of these modes of transportaton were as follows[13]:

                           Avg. # of Deaths/year       Avg. Rate/year
              Airplanes		119.1                       .033
              Trains		  6.5                       .055
	      Buses		 36.3                       .030
              Cars           23,585.0                      1.040
These figures do not include, of course, the costs to society or individuals of medical expenses, insurance costs, property damage, and lost wages.

Accidents can occur because of faulty equipment, weather conditions, human error, or from a combination of causes. But fatigue and sleep deprivation are almost certainly major hidden factors of the human errors that result in accidents. What role, then, does the biological clock play in transportation accidents?

Researchers have found that "the neural processes controlling alertness and sleep produce an increased sleep tendency and diminished capacity to function during certain early morning hours (circa 2-7 A.M.) and, to a lesser degree, during a period in the midafternoon (circa 2-5 P.M.), whether or not we have slept[14]. Several studies of single-vehicle car accidents that have been judged to be fatigue- related have shown two peak times for accidents--a major one between midnight and 7 AM, and a secondary peak between 1 and 4 PM[14].

According to the O.T.A., an average of between 4000 and 5000 fatalities occur each year in accidents involving tractor-trailer trucks. Of the fatalities due to heavy truck accidents, about 80% of those killed are pedestrians or occupants of other vehicles[15]. The National Transportation Safety Board (NTSB) says that the most frequently cited probable cause (31%) of death in heavy truck accidents that were fatal to the driver, is fatigue[16].

Research has shown that truck drivers are susceptible to both sudden fatigue, due to temporary irregularities of the sleep cycle, and accumulated fatigue due to long working hours[15]. In fact, most accidents occur between 4 and 7:30 AM[17]-- well within the time span when drivers are most likely to fall asleep.

The NTSB has made several recommendations to improve truck safety. These include education on the effects of fatigue, on-board recording devices that keep track of driver hours, a review of trucking operations that might create incentives for drivers to violate hours of service regulations, and revision of certain parts of the Code of Federal Regulations to prohibit employers from scheduling shipments which would require drivers to exceed the hours of service regulations[16]. Certainly the other transportation industries could adopt similar strategies to reduce the likelihood of catastrophic accidents caused by fatigue and circadian desynchrony.