Hours of Service and Truck Crash Risk

A case-control study of 231 truck crashes (and 462 controls) was completed with data from three trucking companies from 2004, when new hours-of-service (HOS) regulations went into effect in the United States. Analysis using time-dependent logistic regression indicates that increased crash risk is associated with hours of driving, with risk increases of 50% to 260% compared with the first hour of driving. These findings help to provide a baseline estimate of crash risk relationships for this HOS policy. A series of models indicates that the pattern of crash risk is different for nonsleeper operations and for sleeper schedules. Models of nonsleeper operations indicate that crash risk is strongly associated with multiday driving somewhat more than with hours of driving. Models of sleeper operations indicate strong association of crash risk with hours driving. These findings, though consistent with many results from similar modeling conducted with 1980s data, are subject to important limitations. The small sample size in many cases likely contributed to the relatively high estimates of crash odds (e.g., often in the range of 100% to 200% increases) and to an inability to identify clear trends in some variables. Ideally, this study should be repeated with additional firms over a longer time period. In particular, collecting driver data that cover at least 2 weeks of driving should allow for a much better understanding of the effect of any restart policy. The effects of extended driving, however, strongly suggest that a change back to the 10-h maximum should be considered in any future HOS adjustments.