Fatigue

Predicting Fatigue in Commercial Drivers

You're on your way to Prince George from Hixon. It's almost dawn, and except for you and a large transport truck ahead, the long flat stretch of road is deserted. The truck has kept a steady pace for the past 50 km, but now you notice it seems to be drifting into the other lane from time to time.

You start feeling nervous, and you leave more distance between you and the truck. Your intuition is right - the truck drifts to the right this time, catching a wheel in the soft gravel at the side of the road. It tries to jerk back onto the pavement. As you slow your own vehicle, the truck rolls onto its side, into the ditch. You pray the trucker is OK, and feel thankful that you stayed far enough behind to avoid a collision with the runaway truck.

Scenarios like this still occur on North American highways. In an attempt to reduce driver fatigue, Hours of Service (HOS) regulations were developed. But, as in most cases, this trucker's logbook showed he had not violated the regulations and had recently taken the required 8 off-duty hours.

ICBC wants to learn more about why, despite HOS regulations, fatigue may be a factor in up to half the commercial vehicle crashes. Their aim is to help reduce driving risk for all motorists. Research suggests a factor that may play a role in fatigue is a sleep disorder called obstructive sleep apnea (OSA). OSA is characterized by excessive loud snoring and periodic interruption of breathing, which reduces both the amount and quality of sleep. Phillipson (1993) reported that the main effect of OSA was excessive daytime sleepiness.

ICBC designed this study to determine if a screening instrument could be developed to identify which commercial drivers could benefit from treatment for OSA. The first phase of the study produced some interesting results.

The study interviewed commercial truck drivers, asking them to rate how rested they felt or how well they felt they had slept. In comparing on-duty and off-duty sleep patterns, ICBC found that the quality of sleep rather than the amount of sleep, played a key role in how rested the truckers felt. However, although symptoms of the sleep disorder (especially loud snoring) were found among a significant number of long-haul drivers, OSA alone was not found to be the best predictor of sleep quality.

A driver's response to work pressures proved to be the best predictor of which truckers would most likely ignore signs of drowsiness. Some drivers may fear negative reactions from others if they are late delivering their loads. These drivers may continue to drive in spite of feeling sleepy. Drivers who think others will see them as good workers and more worthy of respect if they always arrive on time, are especially likely to continue driving.

photo courtesy of AAA

Foundation for Traffic Safety Canada and the US are currently reviewing Hours of Service regulations. The results of this study suggest that sleep quality should also be considered in revising the regulations. The trucker in our story had just been off-duty for 8 hours. However, since he is a long-haul driver, he slept in the sleeper berth of his truck and was frequently interrupted by loud noises. He was worried about getting his load to its destination on time, so his symptoms of obstructive sleep apnea increased. He did not get a restful sleep. But, as soon as the regulations permitted him to drive again, he was back on the road. ICBC is continuing to study the various factors that contribute to driver fatigue. Results of these studies may be used to revise Hours of Service regulations, validate fatigue-detection devices, prepare educational campaigns directed at all road users, or to screen or establish work schedules for commercial drivers.

References: Phillipson, E.A. 1993. Sleep Apnea: A Major Public Health Problem. The New England Journal of Medicine. 328(17); Editorial.

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Fatigue

Predicting Fatigue in Commercial Drivers

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