A popular definition of workload is given by O’Donnell and Eggmeir, which states that “The term workload refers to that portion of the operator’s limited capacity actually required to perform a particular task” [1]. In the vehicle environment, the “particular task” refers to both the vehicle control, which is the primary task, and other secondary activities such as listening to the radio. Three major types of driver workload are usually studied, namely, visual, manual, and cognitive. Auditory workload is not treated as a major type of workload in the driving context because the auditory perception is not considered as a major requirement to perform a driving.
