Driver fatigue among long-distance truck drivers is a significant and long-standing safety issue. Research has shown that fatigue is not only "common" but also an "important crash factor" in crashes involving heavy trucks. Addressing this problem, the Federal Highway Administration (FHWA) is currently reviewing and revising the "hours-of-service (HOS) regulations" that govern long-distance commercial truck driving. Truck drivers report that they often violate these regulations, and studies have identified a number of causative factors for these violations--including scheduling issues, low pay, and the relationship between time of day and fatigue.

Research in areas of highway safety typically draws on data maintained by government agencies, but these databases often do not represent a complete or accurate picture of a given safety issue. Such is the case with "drowsy driving" among long-distance truck drivers, which is believed to be "underreported as a crash factor." To obtain a more comprehensive picture of this driver-fatigue problem, a recent study surveyed long-distance truck drivers to "gather in-depth information on work and rest patterns and experiences with sleepiness-related driving."

The results of the study were documented by Anne T. McCartt, Mark C. Hammer, and Sandra Z. Fuller in their article "Work and Sleep/Rest Factors Associated with Driving While Drowsy: Experiences Among Long-Distance Truck Drivers," The Association for the Advancement of Automotive Medicine published the report in their 41st Annual Proceedings, Orlando, FL, November 10-11, 1997. Results "confirm[ed] that driving while drowsy is a common experience for [truck] drivers." Nearly two-thirds reported episodes of drowsy driving within the past month, and almost 5 percent indicated driving this way on most, if not all, days. Nearly half had fallen asleep at the wheel at some point in their travels, and about a fourth reported doing so at least once during the past year. Frequent violations of the HOS regulations were also reported on the survey.

METHODS

During the spring of 1997, 593 truck drivers were interviewed on New York's interstate highways. The majority were interviewed face-to-face at "private full-service rest stops." Researchers also did interviews at "public full-service and limited-service rest areas" and at "routine truck safety inspections" conducted at public limited-service rest areas. Random sampling was used at all the sites. Criteria for drivers who chose to participate included (1) at least six months' experience driving a tractor-trailer, (2) occasional trips of two or more days, and (3) a minimum of 50,000 miles per year driven for work. Participating drivers received a $5 voucher for food, beverages, or other refreshments. Participation rates ranged from a low of 64 percent at public full-service rest areas to a high of 91 percent at private full-service truck stops.

The survey questionnaire addressed a number of possible characteristics related to drowsy-driving behavior. In addition to those characteristics listed in Table 1, the survey asked about union membership and the presence of a computer in the truck. The survey also solicited significant information about routine work schedules and habits/patterns of sleep and rest. The survey used the Epworth Sleepiness Scale (ESS) to measure "the driver's general daytime sleepiness." Researchers asked drivers to rate their likelihood of falling asleep in eight different situations. Opinions were also solicited from drivers about the effectiveness of proposed measures and regulations to reduce drowsy driving among truck drivers.

RESULTS

Table 1 lists outcomes for the driver and job characteristics surveyed. Table 2 lists the frequency of violations of the HOS regulations. Almost 20 percent of drivers reported that on U.S. roads they "always or often" exceed the ten-hour driving limit in the regulations. Close to a fifth "always or often" are off-duty for fewer than eight hours, and just over 21 percent "always or often" drive longer than their records indicate.

Table 3 records the frequency of drowsy driving and instances of falling asleep at the wheel. As indicated, close to 50 percent of drivers reported having fallen asleep at the wheel of their truck, and 65.7 percent reported at least one occasion of driving while drowsy during the last month.

The study also examined job and sleep/rest factors associated with drowsy driving during the past month. Some of these factors included (1) the usual duration of trips, (2) driving in the evening and at night, (3) overnight trips, (4) the number of off-duty hours of sleep, and (5) the number of hours both worked and driven in a seven-day week. Results showed that independent truck operators had fewer episodes of drowsy driving, and truck drivers whose trips typically last 6-14 days had more frequent drowsy-driving experiences. Other factors associated with more frequent episodes of drowsy driving included (1) driving at night, (2) working or driving longer than a seven-day week, (3) a varying schedule, (4) violating HOS regulations, (5) frequent napping, and (6) poor quality of sleep while on the road. The ESS showed that "a higher level of daytime drowsiness was related to more frequent drowsy driving."

In addition, the study examined the "hypothesized" job and sleep/rest factors associated with falling asleep at the wheel over the past year--most of which were similar or identical to those factors associated with drowsy driving. "Method of pay" was one factor not included in the drowsy-driving list, and results suggested that drivers who were paid by the hour, and those who were owner-operators with a long-term lease, were less likely to report episodes of falling asleep at the wheel. In addition to tight delivery schedules, factors associated with falling asleep at the wheel included (1) more work hours in a seven-day week (with more HOS violations), (2) night driving, (3) napping on the road, and (4) dividing off-duty rest into two periods.

Table 4 lists the opinions solicited from truck drivers on proposed measures to reduce drowsy driving. As indicated, truckers were supportive of, among other things, more education on the inherent dangers of drowsy driving and on the benefits of required rest breaks. Truckers were generally not supportive of limits on nighttime driving and requiring more than eight hours of off-duty time.

CONCLUSIONS