Driver Performance and Memory for Traffic Messages:
Effects of the Number of Messages, Audio Quality, and Relevance

Jill Fleming, Paul Green, Stewart Katz

June, 1998

In this experiment, 32 licensed drivers (16 young, 16 old) drove on an expressway. On each trial (96 per subject), 1 to 3 traffic messages containing 6 to 14 items were presented. ("I-94 eastbound at Southfield freeway, continuing construction, right lane blocked, 3 mile backup."). Imagining they were driving from Ann Arbor to Detroit on I-94, subjects identified messages relevant to that route and recalled them. Messages were either of good or poor audio quality (to simulate poor reception).

Drivers familiar with the route correctly recognized about 85 % of the relevant messages. Typically 4 items were recalled regardless of message length, with the road and crossroad being most common. Drivers recalled the direction to which the message pertained (e.g., I-94 east) only 39 percent of the time. Drivers believed the traffic information system was safe and useful to listen to while driving (approximately 9 on a 10-point scale) and would pay $177 on average for one, though most subjects were not willing to pay anything.

Of the message characteristics, message audio quality had the largest adverse impact on performance (increasing speed variance). Differences were also found between (1) driving, (2) driving while listening to messages (slight increases in speed variance), and (3) driving while speaking with the experimenter (further increases in speed variance). This is in contrast to claims that dealing with auditory information while driving has no impact on driving workload and is not a safety concern.

Graphical Abstract (.pdf) | UMTRI-98-22 Full Report (.pdf)


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