Abstract
In order to investigate the possibility of constructing a device that tells the driver if he is still fit enough to drive, a research-project was set up to investigate the influence of monotony on the drivers' performance. A drive-simulator was used with a regularly repeated route to increase monotony. To validate the results of this main test, driver on real roads were also part of the research project. It was found that the precision of the control of the car was deteriorating soon. This was, however, not so much the case on the road with its real dangers.