Driver state and mental workload

Mental workload plays a central role in driver behavior. Unlike physical workload, mental workload is difficult to quantify as it is the result of the interaction between the task to perform, that is, the task demands, and the capacity to perform, that is, the mental resources. While the first can be quantified, the second—as of today—cannot. Still, within individuals and for homogenous groups, judgments about mental workload can be made. Driver state has a large influence on mental workload, and the two concepts cannot be considered separately: deteriorated driver state increases mental workload as the driver has to invest more effort to maintain performance. This chapter addresses the concepts of driver mental workload and driver state and how to assess them, with special attention to the effects of automation on driver state and workload.