We distinguish between fatigue caused by the demands of the driving task itself (see Hancock & Desmond, 2001) from the standard traditional approach that links fatigue predominately to the lack of sleep. Fatigue can be caused by two sources: (1) the driver's initial state before starting the drive, or (2) the characteristics of the drive and the road environment; both sources can have a cumulative effect. It is not clear what principles are involved in making one road environment more prone to

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... nducing driver fatigue than another. For the purpose of the current presentation we provide empirical data on road environment and driver fatigue summarized from a series of three experiments that the first author has conducted at Ben-Gurion University (see Oron-Gilad, 2003; Oron-Gilad, et al., 2001) . Those are examined in relation to the Hancock and Warm (1989) model of adaptability. The most significant and consistent findings of the three experiment is in the way that fatigue is reflected in driving performance across different road environments. These findings suggest that drivers are flexible in the way they handle fatigue over the course of time. They can adopt different strategies to compensate for their performance decrement, by focusing efforts on critical elements of each different type of roadway. Understanding of this dependency of fatigue symptoms on road conditions is of especial relevance to designers of technological fatigue countermeasures as well as those of future roadway systems.