Evaluation of Automotive Control-Display System by means of MentalWorkload

The effects of age, task difficulty on performance and mental workload were discussed in order to provide design guideline of automobile display that is friendly to older adults from the viewpoints of mental attention, speed and accuracy. A dual-task experiment was conducted in which the primary task was first order tracking. The secondary tasks included selection of function (easy condition), and control of an air conditioner, the operation of a radio, and the operation of a CD/MD (difficult condition), by means of a steering wheel mounted switch. The display was arranged in front of a participant. Age affected the performance measures and heart rate variability (HRV). As for the young adults, the task completion time did not differ significantly among easy and difficult (one-, two-, and three-layered) conditions. The performance of older adults was affected by task difficulty. The HRV measures such as CV (coefficient of variance) and RRV8-3 during the task showed different tendency between young and older adults. As for the young group, the HRV measures did not differ significantly between the four task levels (easy, one-, two-, and three-layered). This confirmed that the task difficulty did not induce different mental workload to young adults. On the other hand, as for the older adults, the HRV measures tended to increase with the increase of task difficulty. Although it appears that mental workload was lessened with the increase of task difficulty, such an interpretation was contradictory to the results on performance. This phenomenon was interpreted that the difficult task condition was overloaded for older adults, and was beyond the limit of mental effort. Based on the results, it could be concluded that the difficult task condition is not proper for older adults.