14: Fatigue and Driving

Although we all know it when we feel it, fatigue is not that easy to define. It is a hypothetical concept that cannot be directly observed. As such it is often defined as “a biological drive for recuperative rest” (Williamson et al., 2011). In more practical terms, nearly 70 years ago, Bartley and Chute (1947, as cited by Brown, 1982) attempted to define fatigue by a list of what it is and what it isn’t. This list of identifying features is reproduced in Table 14-1.

In short, according to Brown (1982) it is a “subjective experience of tiredness and unwillingness to continue working.” The obvious shortcoming of this definition is that it is based on purely subjective experiences and therefore very difficult to study in a scientific manner. Unfortunately not much has changed in this respect over the past half century, and there is still no agreed-upon definition of fatigue among researchers (Ǻhsberg and Gamberale, 1998; Belz, Robinson, and Casali, 2004; Di Milia et al., 2011; Williamson et al., 2011; Phillips, 2015).