A quick look at “Predictors of Psychostimulant Use by Long-Distance Truck Drivers” by Ann Williamson in the American Journal of Epidemiology.

An Australian study finds that paying truck drivers by the job (instead of by the hour or week) leads to increased driver use of amphetamines and other stimulants, which is associated with increased risk for highway crashes.

Anne Williamson’s analysis of self-reported stimulant use among truck drivers found between “one in five and one in three drivers reported using stimulants at least sometimes” and “stimulant drug use was twice as likely for drivers who had the greatest problem in managing fatigue and was two to three times more likely for drivers paid on a payment-by-results or contingency-payment basis.”

So, truckers whose income rises if they complete the job faster have a strong financial incentive to drive long hours without stopping. When these drivers have trouble staying awake, they are more likely to take stimulants. The impact is well known – several studies have found taking stimulants like amphetamines is associated with greater risk of involvement in a fatal crash.

Williamson sums up the study and its implications with clarity and insight:

In conclusion, finding a relation between drug use and problems with managing fatigue may not be surprising because drivers who have the biggest problem with fatigue might be expected to need to take drugs. The influence of productivity-related payments on drug use is more surprising, especially because this factor had a stronger effect than a range of other factors that could have played a role. This study highlights important implications for designing effective interventions to reduce drug use while driving. The results show that strategies to reduce the use of stimulants in the long-distance road transport industry must focus on reducing fatigue for long-distance truck drivers, but they also show that this goal will probably be achieved only if the external pressures of productivity-based payments are removed from the industry. When drivers are encouraged to complete more trips because they can earn more money, fatigue will be a natural consequence. Stimulant drugs will continue to be used in lieu of sleep; they are one of the few effective strategies available for drivers to stave off fatigue under these circumstances. Changing the incentives for drivers to encourage fatigue reduction is clearly a primary target.

Citation: Williamson A. Predictors of Psychostimulant Use by Long-Distance Truck Drivers. Am. J. Epidemiol. 2007 166:1320-1326.