People who are tired are less attentive and will therefore react less quickly and less adequately than people who are not tired [2] [3] [4]. Fatigue also affects mood and thus behaviour: tired people get irritated and frustrated more easily [4] [5].
A lot of research has been done into the effect of fatigue on driver behaviour. Most of these studies have been done by means of computer tasks or driving simulators in laboratories (for example [6] [7]); some of them, however, in actual traffic (for example [8]). For these studies, people are kept awake for a long time to attain sleep deprivation, or they have to continue driving for a long time. The effects may thus be summarised [2] [3] [4]:
- reacting more slowly;
- steering less accurately;
- wider variations in headway distance and speed.
There are some indications that drivers try to compensate for fatigue effects by complicating the driving task (higher speed, shorter headway distances) or, contrarily, by applying wider safety margins (low speed, longer headway distances) [3].
