The authors performed a laboratory study using simulated road scenes and simulated automobile head-up displays (HUDs) to examine the effect of HUD location on a driver's ability to discriminate the presence or absence of a pedestrian in or near the path of the vehicle. They showed subjects brief presentations of road scenes with HUDs superimposed at three different positions: 4, 9, or 15 degrees below the horizon. Subjects had to perform two tasks for each presentation, one based on the road scene and one based on information in the HUD. The authors' intent was to asses how HUD location affected a driver's sensitivity to the outside environment while he or she was paying attention to the display. The authors therefore instructed subjects to emphasize accuracy on the HUD task to the extent that the demands of the two tasks conflicted. Because the authors believed that there would be important differences between young and old subjects in the effect of HUD location, they included subjects in two age groups, which averaged 21.3 and 66.1 years old, respectively. Performance on the map task was only slightly affected by HUD location, whereas performance on the pedestrian task deteriorated markedly when the HUD was further below the horizon. This is consistent with the instructions for subjects to maintain high accuracy on the HUD task. The change in performance on the pedestrian task was significantly greater for the older than for the younger subjects. This finding is consistent with other results showing that older people have more difficulty in visual divided-attention tasks. These results provide quantification of the benefits of HUDs in maintaining sensitivity to the outside environment when a driver is attending to vehicle display. The larger question of how drivers should distribute attention between the road and vehicle displays for optimum safety is not addressed by this study.
Samenvatting