Usability evaluation of symbols in digital cluster for drivers with color vision deficiency

Digital clusters have been adopted as displays in vehicles, and various driving information is presented through the digital clusters with different colors. However, drivers with color vision deficiency (CVD) face difficulties in recognizing the information conveyed through color, which might lead to serious traffic accidents. In this paper, the usability of symbols in automobile digital clusters was evaluated from the perspective of people with CVD, and alternative designs were proposed and validated to improve recognition of the symbols. Twenty-seven participants with CVD and twenty-one participants with normal color vision (NCV) were recruited to investigate the influence of design elements, such as symbol color, stroke width, cluster background color, and adjacent symbol color. The choice reaction time and error rate were measured, and the perceived importance and visibility were collected using a questionnaire. As a result, the following four effects of symbol designs on the usability and recognition were identified: (1) if the existing color profile for symbols is applied, the symbol recognition was improved by modifying symbol design elements (e.g., stroke width); (2) For the symbol stroke width, a stroke width-to-height ratio of 0.12 or more was recommended; (3) Gray color is recommended for the background color, but lighting a red symbol on a gray background should be avoided for the participants with CVD; (4) When presenting a symbol adjacent to another one, presenting in red-red, green-green, orange-red, and orange-green combinations should be avoided. The results of this study can be used as reference materials when developing vehicle display interfaces that are accessible to all users including people with CVD.