ANCOVA: Analysis of Covariance; BMI: Body Mass Index; CI: Confidence Interval; RoM: Range of Motion; SPSS: Statistical Package for the Social Sciences.

Automotive gear shifters are among the most important control devices in driving tasks, and their user-centered design has a direct impact on the driving performance and safety. In recent years, shift-by-wire systems with electronic shift buttons have replaced conventional transmission systems due to their advantages, such as the ease of shifting and space utilization inside vehicles. However, there are no minimum requirements or specific regulations for electronic shift button layouts. Thus, different car manufacturers and models have adopted different layouts, and this in turn has induced the risk of driver confusion/error in the shifting operation. Therefore, this study aimed to evaluate the ergonomic performance of different electronic shift button layouts and examine the variance in performance depending on driving experience. Here, 21 survey respondents with different levels of driving experience subjectively evaluated 12 different shift button layouts for 7 ergonomic evaluation measures (accuracy, convenience, rapidity, learnability, intuitiveness, safety, and preference). The outcomes of the study elucidate ergonomic layouts that receive high rankings in each driving experience group (all, novice, and experienced drivers) and principles that should be considered when designing shift button layouts for each group. These findings are expected to contribute to the ergonomic design and international standardization of shift button layouts, thereby preventing driver confusion/errors and improving road safety.

This study compared obese and non-obese drivers in the preferred seat and steering wheel setting and preferred driving posture. Twenty-one extremely obese and 23 non-obese drivers participated. Each participant determined the most preferred setting of the interior components using an adjustable vehicle mock-up; the preferred components setting and corresponding preferred driving posture were recorded. The participant groups exhibited significant differences in the preferred interior components setting. The obese group created larger steering wheel-seat space than the non-obese, with greater rearward seat displacement, more upright steering wheel angle and smaller steering wheel column displacement. It also exhibited more upright seatback angle deemed necessary for facilitating steering wheel reach with the increased steering wheel-seat distance. The between-group differences in the preferred driving posture were less pronounced: no significant group mean angle differences were found except for the elbow joint angles. Also, the mean hip joint centre positions did not significantly differ. Practitioner Summary: To contribute to larger driver packaging, this study compared obese and non-obese drivers in the preferred vehicle interior components setting and driving posture. The obese group created significantly larger space between the steering wheel and seat than the non-obese, through interior components adjustments. The between-group postural differences were less pronounced.