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When should auditory guidance systems tell drivers to turn?

In: Human Factors and Ergonomics Society. 39th Annual Meeting. Designing for the Global Village. Proceedings. Volume 2. Santa Monica, Human Factors and Ergonomics Society, 1995, p. 1072-1076; DOI: 10.1177/154193129503901702

Authors: Paul A. Green, Kellie George

This two-part experiment examined how far from an intersection an auditory route-guidance system should present the final turn instructions (e.g., “Turn right.”). In part 1, 48 drivers followed instructions from a simulated in-vehicle navigation system (“In approximately 2 miles, turn right at the traffic signal”), responding “Is this it?” when they thought they had reached the desired intersection. In response, the computer gave the appropriate guidance (“No, continue…” or “Turn…”). In part 2, they repeatedly approached 2 different intersections. Feedback from previous trials (“too far,” “too close,” “OK”) was used to adjust when messages (e.g., “Turn left.”) were presented. Regression analysis revealed that last turn messages should be provided approximately 450 feet before an intersection (approached at 40 mi/h), with that value being adjusted 15 feet for each mile per hour change. Adjustments are also made for gender (plus or minus 56 feet), age (plus or minus 60 feet), and turn direction (plus or minus 48 feet).