Differential sensitivity of self-reported driving and collision measures to aspects of shiftwork, sleep, and fatigue

Sleepiness, fatigue, and shiftwork are three aspects of daily life that might affect individuals' safety when driving. Driving behaviours are commonly assessed via self-report measures. In this study, different self-reported measures of driving behaviours are compared to test their sensitivity to measures of sleepiness, fatigue, and night shiftwork. Police shiftworkers from English forces completed a survey that included questions about shiftwork, sleep, fatigue, and included three measures of driving behaviour: The Driver Behaviour Questionnaire (DBQ - Lawton et al., 1997; Reason et al., 1990), Smith's (2016) measures of poor and fatigued driving, and self-reported collision frequencies. Hierarchical regressions confirmed that the driving behaviour measures were differentially sensitive to aspects of sleepiness, fatigue, and shiftwork. Responses to Smith's components of driver fatigue and risk taking, and questions on collision frequencies, but not responses to the DBQ, could be predicted from the proportion of night shifts a person worked. Conversely, only the DBQ was sensitive to fatigue as a predictor of poor driving. All measures were sensitive to aspects of sleepiness and the extent to which it predicted driving outcomes (Adj. R²) differed between scales. Self-reported collision data was least sensitive to contexts of shiftwork, sleepiness and fatigue and such data should be used cautiously to explore effects of sleep and shiftwork on driving behaviour. The present findings highlight the importance of using scales that are sensitive to the context of investigations (e.g., shiftwork). Relying on inappropriate scales could lead to the underreporting of poor driving behaviours in sleepy and shiftworking drivers.