Abstract: A vast majority of traffic accidents can be related to an inadequate workload level for the driver. Much progress has been made in automated in-vehicle systems and related human-machine-interfaces, aiming to reduce workloads. However, research has shown that automation may fail to alleviate the workload and can even introduce a new source of workload due to the need to attend to new tasks, and thus needs to be carefully tested before being implemented on vehicles. Driving simulators can be a viable alternative to on-road tests since they provide adequate experimental control and do not jeopardize driver safety. However, it must be shown that there is correspondence between the behaviour in the simulator and the behaviour on the road, that is the simulator absolute (the numerical values obtained under simulation and on-road are the same for specified variables) and relative validity (the extent to which the direction and magnitude of behaviours are comparable between the two settings). In this study we investigated the validity of a driving simulator-based experimental environment for research on workload measures by comparing behavioural and subjective measures of workloads of the same large group of participants in a simulated and on-road driving task on the same route. Consistent with previous studies, mixed support was found for both types of validity, although results suggest that allowing more and/or longer familiarization sessions with the simulator may increase its validity. Simulator sickness also emerged as a critical issue for the generalizability of the results.
Keywords: driving simulator, instrumented vehicle, workload, validity.