Abstract
The purpose of this study was to determine a stress threshold for drivers under various combinations of discrete and tracking workload. For example, if a driver was given a tracking (steering) workload of 50%, the objective would be to determine the largest percentage of discrete workload (such as sign reading) he could handle simultaneously. The 15 subjects in the study first carried out a series of tracking tasks, and the workload on each difficulty level was measured with a secondary task. They then executed a number of discrete tasks, and the workload on each difficulty level was measured. Various workload levels were then combined in an effort to discover the stress threshold for different combinations of discrete and tracking tasks. Study results indicated that subjects are unable to simultaneously execute two tasks, each of which occupies 50% of their attention when executed alone. A regression analysis was performed on the data to determine what levels of tracking workload can be executed simultaneously with various levels of discrete task workload.
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