Automotive Head-Up Displays (HUDs): Considerations for Color-limited Users

Abstract

Head-Up-Displays (HUDs) were initially developed for use in aircraft to provide the pilot with essential aircraft flight information aid while flying. The HUD allows the pilot to view primary flight information overlaid on the external scene without the necessity of looking down inside the cockpit at their instruments. Thus they can maintain their gaze outside of the cockpit during critical phases of flight like landing while still having access to critical flight information like altitude, speed, and heading. HUDs have also been adapted to ground vehicles. The first production vehicle with a HUD was the General Motors Cutlass Supreme, in 1988 (Weihrauch et al., 1989). Over 30 companies have implemented this technology into select vehicle models (Korentsides et al., 2021). This technology is also gaining traction among aftermarket manufacturers that offer hardware that owners can integrate into their vehicles. Information typically displayed on a HUD includes safety alerts, navigation directions, and the status of vehicle parameters such as speed. The systems allow drivers to customize the information they see displayed and they can change the information based on the situation. Most HUDs employ a limited color palette of red, green, yellow, and sometimes blue to code information and to represent hazards or risks. Typically alphanumeric information in aviation and automotive applications is rendered in bright green that is visible across a wide range of external illumination conditions. The use of color in consumer products poses some challenges because approximately 8% of the male population and a much smaller percentage of women have color deficiencies that affect their ability to discriminate among some hues including the widely used red, green, and yellow hues (Chaparro & Chaparro, 2017). By recognizing this issue, designers, engineers, and human factors practitioners can ensure that all users, irrespective of their visual status, can use their systems safely. In this paper, we explore different strategies to ensure that information is accessible to users regardless of their visual status. The strategies include using redundant coding so that critical information is encoded using multiple stimulus dimensions (e.g., brightness, color, saturation, texture, font, etc). We also discuss the use of software applications that simulate how any color combination might appear to persons with different color limitations allowing designers to evaluate different color codes or palettes.