Comprehensive analysis of different text sizes on in-vehicle displays from the perspective of arcminutes to promote intelligent information display and driving safety

Highly legible text presented on in-vehicle displays contributes to less distraction from the driving task. Thus, it can promote more intelligent information display and driving safety. However, there are limitations to the scenarios in which previous experimental findings can be applied. Here, we employed the arcminute of the text as a more comprehensive unit representing text size and developed a more precise procedure to investigate legibility. Moreover, we jointly investigated the effect of the arcminute of the text (8’, 13’, 18’, 26’, 36’, 50’, 70’, and 80’), effect of state (static or driving), effect of text display position (instrument panel or control panel) and effect of age (young drivers or elderly drivers) on the legibility of the text simultaneously. Forty-nine participants (26 young and 23 elderly) were recruited in our experiment, and they were required to complete the simulated driving task and secondary task on in-vehicle displays. The results of the driving task suggested that an arcminute of the text equal to or greater than 18’ can assure the stability of the vehicle according to the standard deviation of the longitudinal speed. In the secondary task, an arcminute of the text equal to or above 26’ led to fast and accurate reading. The text reading accuracy and speed are relatively high for smaller arcminutes (< 26’) in the driving state and on the control panel compared to those in the static state and on the instrument panel. The subjective evaluation showed that the main effect of the text arcminute was significant. Drivers evaluated greater arcminutes of the text as clearer and more comfortable than smaller arcminutes of the text. This study provided a theoretical framework through which more effective factors can be considered in the text legibility of in-vehicle displays.