Visuospatial Workload Measurement of an Interface Based on a Dual Task of Visual Working Memory Test

Guidelines devised to ensure that multiple and highly functional in-vehicle information systems (IVISs) are designed to present a distraction-free interface at the same time, need to consider the safety, functionality, and usability of image displays. However, no guidelines exist for quantitatively assessing drivers' cognitive workloads, and this includes usability and memorability. In this paper, we propose a method to measure drivers' visuospatial workload quantitatively. The method is incorporated in various interface tests including driving and human machine interface evaluations. The results indicated that the success rates of visuospatial working memory tasks can be used to rank the relative difficulties of the tasks, and the ranking order of these rates tended to be similar to that of the subjective difficulties.