Colleen Serafin, Cathy Wen, Gretchen Paelke, and Paul Green

April, 1993

This report describes three experiments to develop an easy to use car phone interface. In the first experiment,19 people at two local secretary of state driver licensing offices gave their preferences for button labels and abbreviations. The second experiment with seven participants concerned label abbreviations. The following labels (and abbreviations) are recommended: power (Pwr), Call, End, delete (Del), memory (Mem), and recall (Rcl).

Twelve drivers (six under 35 years, six over 60 years) participated in the third experiment, a laboratory study, in which they operated a simple driving simulator and used a car phone. The phone was either manually dialed or voice-operated, and the associated display was either mounted on the instrument panel (IP) or was a simulated head-up display (HUD). Phone numbers dialed were either local (7 digits) or long distance (11 digits), and could be familiar or unfamiliar. In addition, there were four conversational tasks, two of which were fairly ordinary (listening, talking) and two of which required some mental processing (loose ends, listing).

Driving performance (voice--5.7 inches; manual--6.1 inches) and dialing times (voice--9.2 seconds; manual--10.7 seconds) were better with the voice-operated phone than the manual phone using either the IP display or HUD. In addition, younger drivers outperformed older drivers with regard to both driving (younger--5.6 inches; older--6.0 inches) and dialing performance (younger--7.4 seconds; older--12.6 seconds). Thus, voice appears to be an effective way of improving the safety and performance of car phone use, but the location of the display is not important. The benefits of voice are particularly noticeable for older drivers.

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