The primary objective of this report is to develop a better understanding of how the scheduling practices of motor carrier firms affect driver fatigue. The basis of this empirical research is a commercial driver fatigue model that includes driving environment (i.e., regularity of time, trip control, and quality of rest), economic pressures exerted on drivers (from customers, carriers, and the drivers themselves) and company safety practices as key factors in explaining driver fatigue. The model utilizes two measures of fatigue: frequency of close calls due to fatigue and driver perceptions of fatigue as a problem. Crash involvement is used to evaluate general safety performance.
Three separate studies were conducted. First, the influence of driving environments alone on fatigue among over-the-road truck drivers was tested through a survey of 502 drivers at five geographically dispersed truck stops. A typology of driving environments was developed and the percent of drivers in each category was determined. It was found that a large number of drivers are in the “high fatigue risk” categories. Regression analysis identified starting the work week tired and longer than expected loading and unloading time as significantly related to both measures of fatigue. Regularity of time, regularity of route, and hours of uninterrupted sleep were each statistically significant factors for one fatigue measure.
Next, the complete model was tested on a random sample of 279 drivers at 116 trucking companies and 122 drivers at 66 motor coach companies, which was then stratified on the basis of safety performance (i.e., SAFESTAT ratings). Data for these two studies were generated from surveys of drivers, safety directors, dispatchers, and top management at the sample firms. In the truck company study, starting the workweek tired was the single most significant factor related to fatigue. Other significant fatigue-influencing factors were difficulty in finding a place to rest and shippers’ and receivers’ scheduling requirements (including loading and unloading). Company safety practices that mitigated driver fatigue were carrier assistance with loading and unloading, carrier efforts to minimize nighttime driving, and driver voluntary attendance at corporate safety and training meetings.
In the motor coach company study, the most significant factors related to driver fatigue were starting the work week tired, driving tired to make a good income, and pressure on drivers to accept trips. Two safety measures – drivers’ perceptions of their company’s safe drivingculture and policies, or attempts to minimize nighttime driving – mitigated some of the factors that adversely affect driver fatigue
