Detecting and Reading Text on HUDs:
Effects of Driving Workload and Message Location

Omer Tsimhoni, Paul Green, and Hiroshi Watanabe

May 2001

This paper describes the second in a series of studies to identify best locations for presenting information on an automotive head-up display (HUD). A total of 16 participants (8 under age 30, 8 over age 65) drove a simulator (at 3 controlled levels of driving workload) while responding to messages appearing at 8 locations on a HUD. Depending on the condition, participants either pressed buttons to indicate the gender (male, female) of a first name shown on the HUD or detected the appearance of a scrambled name. The overall pattern of the results was generally similar for both young and old drivers, though the driving performance of older men was better (less variable) than other age-gender groups. Their responses to HUD messages, however, were slower, and they committed more errors.

In contrast to the prior study, detection time was not significantly affected by HUD position. However, mean responses times for the reading task were significantly affected (1100 ms for center positions straight ahead versus 1250 ms for outer positions 10 degrees to either side).

Across the limited range of driving workload levels explored, detection time increased by as much as 140 ms (25%) and information was more likely to be missed in the higher workload condition. Mean response time in the reading condition increased by 90 ms (7%). Driving performance was only degraded when the HUD appeared at the center position. The position most preferred by participants was at eye level, 5 degrees to the right of the center, with the center and 5 degrees to the left of the center as alternatives.

Overall, the central location and other locations within 5 degrees of straight ahead gave the best performance and were more likely to be preferred, followed by the other two locations on the bottom row. The particular location that is best for a specific application depends upon the relative importance attributed by designers to the measures collected.

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