Intergroup research initiative "Head-Up-Displays"
Head-up displays (HUDs) are well established in aircraft cockpits. The situation in road vehicles is different. Some car manufacturers propagate the use of HUDs to display velocity measurements along with other traffic information. The expected advantages of this technology include the reduction of the period of time required to read the display, during this eyes-off-the-road time, the driver does not attend to the traffic; further, the time needed for changes in accommodation might also be shortened. On the other hand, distraction by information not actually needed, or the difference in presentation mode, such as digital vs. analog, may be disadvantageous.
Published results from eye movement physiology can be used to estimate the eyes-off-the-road times and to compare them between the HUD and conventional instrument design. These physiological arguments predict that the reduction in the eyes-off-the road time at the HUD (versus conventional display) for the task of reading the velocity instrument is about 100 ms, which is considered marginal and much smaller than reported in advertisement. Further, no specific additional time for vergence eye movements seems to play a role at the conventional display.
Thus, the human vision system seems to be developed ecologically particularly well to perform fast vergence gaze shift with both eyes from far horizontal to near declined targets; this condition also applies to the task of reading the velocity display in the conventional setup. Possible advantages of HUDs in a car are most likely found in other aspects than the replacement of conventional instruments.