Measures of driver behaviour and cognitive workload in a driving simulator and in real traffic environment : experiences from two experimental studies in Sweden.

The use of ITS (Intelligent Transportation System) in general is increasing in road traffic with external demands on driver attention and cognitive functioning. Also in-vehicle systems such as navigation and onboard PCs with Internet and e-mail connections are on the market in many parts of the world. Two different studies are presented in this paper. These have focused upon mental performance as a result of driving in a tunnel simulation with a route choice task and in a real traffic environment with the effect of various in-vehicle navigation tasks. Results indicate future orientation and road choice problems, as much as 50% of test-drivers missed important road sign information and made critical road choice errors at specific points, i.e. entering the tunnel system from main roads. In the second study, significant effects of visual and visual/verbal but no significant effects of verbal instructions on mental performance were obtained. These results are discussed with respect to requirements regarding suitable standard methods for assessment of cognitive workload caused by external information (i.e. road/tunnel environment) and from in-vehicle systems.