ABSTRACT
Workload assessment techniques are traditionally divided into four major categories: subjective, physio-
logical, performance based, and analytical methods (Meshkati et al., 1992; Wierwille and Eggemeier,
1993). The performance based measurement assumes that any increase in task difficulty will lead to
an increase in demands, which, in turn, will result in degrading performance (Young and Stanton,
2004). Physiological indexes assume that the mental workload can be measured by means of the level
of physiological activation (Rubio et al., 2004). Subjective procedures are based on operator judgments
of the workload associated with performance of a task or system function. Subjective procedures assume
that an energy expenditure associated with task performance is linked to the perceived effort, and can be
appropriately assessed by individuals. Thus, the subjective measures reflect direct opinion of an operator
about the effort required to accomplish task in the context of the task environment, and his or her skill
and experience (Tsang and Wilson, 1997).
