Modeling motor carrier crash risk with variable schedules over multiple days

Management of driver hours of service (HOS) for commercial vehicle operators has been a continual safety challenge. While there are many reasons why managing service hours is a challenging task, one of the most perplexing aspects is the inconsistency in research findings concerning the effect of driving schedules on driver performance and safety. Moreover, few authors mention what specific irregular schedules and night driving time period the driver had driven, even if many authors concluded that nighttime and irregular schedules contribute to significantly higher risk. Furthermore, previous research studies concerning fatigue-related accidents were less focused on multi-day driving patterns than they were on other factors.; This study examines seven consecutive days driving logs for the 1980s and 2004. Moreover, this study juxtaposes these consecutive driving logs with specific driving schedules to evaluate the relative accident risk of each multi-day driving pattern. Moreover, there is a need to understand the relationship between commercial truck driver hours of service and the risk of a crash, particularly correlations with federal hours of service regulations.; A series of time-dependent logistic regression models are used to analyze crash and operations data from two distinct time periods: the mid 1980s and 2004. This study found that accidents are strongly associated with driving time (time on task). Moreover, nighttime driving schedules yield higher accident risk than the other driving schedules. Particularly, drivers who take less rest time between two shifts yield higher accident risk. Also, experienced drivers (greater than or equal to 10 years) have a 15 percent lower accident risk than less experienced drivers (less than 10 years) driving at regular nighttime. However, when drivers have driven for three consecutive days, the regular driving schedules, except for the nighttime driving schedules, and the irregular driving schedules do not show a strong association with driving experience. However, for the experience variable, drivers with more than 10 years of experience have around 40 percent lower crash risk than drivers with less than 10 years of experience. Therefore, the experience is associated with the driving time.; Particularly, the heavy schedule drivers who have driven for many driving hours everyday have little chance to recover from fatigue. The results show that drivers who had driven more than eight hours for three consecutive days (heavy schedule) have over a 25 percent higher accident risk than driver who have driven less than eight hours for three consecutive days (light schedules). When drivers with a heavy driving duration have driven for three consecutive days, the results show that the effect of the heavy schedule is the same for experienced drivers and less-experienced drivers. Therefore, when drivers with heavy driving duration have driven for consecutive days, they may experience a decline in driving performance.; Usually, drivers who use sleeper berth operation (sleep in their trucks) do not obtain the same quality of sleep as if they were sleeping at home. For the 2004 dataset, a series of models indicate that the pattern of crash risk is different for non-sleeper operations than for sleeper schedules. Models of non-sleeper operations indicate that crash risk is strongly associated with multi-day driving somewhat stronger than with driving time. Models of sleeper operations indicate strong association of crash risk and driving time. Interestingly, within sleeper berth operations, there is much less association of crash risk with regular schedules and substantial risk associated with irregular schedules. These findings help to provide a baseline estimate of crash risk relationships for the new hours of service policy initiated in 2004.