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Development of a Test Protocol to Demonstrate the Effects of Secondary Tasks on Closed-Course Driving Performance

To assess the relative distraction potential associated with a variety of in-vehicle tasks, we developed a test protocol that provides an objective basis for demonstrating the tradeoffs between primary and secondary task performance in driving. The protocol includes two summary scores, one representing driving performance and one representing secondary-task performance. Driving performance was evaluated on a 1.3-mile test course, which included straight and curved road segments, a signalized intersection, a simulated work zone, two changeable-message signs, and six unexpected events. Secondary tasks included mental arithmetic, reading, writing, phone dialing, CD changing, route-guidance destination entry, eating, drinking and grooming. Twelve subjects drove an instrumented vehicle for 9 or 10 timed laps of the test course, each while performing a different secondary task or none (baseline). On average, we found a 15% decrement in driving performance scores on laps in which subjects engaged in a secondary task. Driving performance decrements were observed on 88% of these trials. Differences were observed between different secondary tasks. The pilot test results demonstrate the potential usefulness of the test protocol for assessing tradeoffs between primary and secondary tasks in driving.