It is significant that the dangers of driver fatigue have not found an equivalent expression in the public arena as related concerns, such as drunk driving. The reasons fatigue has traditionally played a secondary role in road transport safety research and policy were outlined by Brown (1994), namely: (a) that evidence of a causal influence of fatigue in accidents is often circumstantial, and (b) a lack of political will to research the limitation of the hours of work for professional drivers, but underpinning both is the fact that (c) fatigue is a complex and ambiguous concept with no standard measurement index. The latter absence of definition lies at the crux of the fatigue problem, both in terms of research and policy. A recent survey of drivers in the UK conducted by G. Maycock (1995) revealed that 29% of his survey sample (N = 4,600) had experienced feeling close to falling asleep at the wheel during the previous 12 months. Only 7% of the same sample reported fatigue as a contributory factor in accident involvement (adjusted by Maycock to implicate fatigue in between 9% and 10% of accidents for the sample). The general point is made that experiences of extreme fatigue do not have a one-to-one correspondence with accident involvement. This chapter is concerned with a description and operationalisation of compensatory strategies to cope with fatigue and impairment in more general terms. It is hypothesised that such compensatory mechanisms are based on the investment and conservation of mental effort (Hockey, 1986, 1993, 1997). Furthermore, the measurement of these compensatory mechanisms may constitute an appropriate basis on which to assess the influence of fatigue on behaviour.
Samenvatting