Pii: S1369-8478(00)00021-8

Car drivers appear to reduce their driving speed in high task demand situations. Summala's [Safety Sci. 22 (1996) 103±117]; [in: J.A. Rothengatter, & E. Carbonell Vaya (Eds.), Trac and Transport Psychology: Theory and Application, Pergamon, Oxford, 1997, pp. 41±52] model of behavioural adaptation (MBA) also assumes that drivers increase speed in low task demand situations or attend to additional tasks more. The present study investigated the relation between driving speed and task demands in simulated driving. Participants were observed under three speed conditions, driving fast, driving as if taking a driving test, and following a fast-driving car. The same route was driven twice under each of these speed conditions: once with and once without the concurrent performance of an auditory short-term memory task. All other things being equal, driving fast required more e€ort than driving more slowly, which was not compensated for by better memory performance. This refutes one assumption of the MBA. When following a fast-driving car, participants invested less e€ort than when driving fast. As auditory route guidance messages were embedded within the memory task, participants were forced to attend the memory task in all rides of the Fast and Accurate conditions, but not in the Car Following conditions. This can also explain why the memory task had no e€ect on cognitive e€ort. It is concluded that car drivers prioritise their task goals. Ó 2001 Elsevier Science Ltd. All rights reserved.