Although improving customer satisfaction, driving safety, and the appearance, exterior, and interior design of customers is crucial, detailed investigations regarding comfort in operating levers to adjust a seat are not available. The design and alignment of car seats and levers have various constraints owing to the limited availability of space. Thus, this study aimed to determine the best lever position considering various constraints of vehicles, including safety, space, operability, and anthropometric variability. Subsequently, a relationship with the Kansei score for various classes of participants, such as low-torque occupants (female and elderly) and high-torque occupants (male), and users with a wide range of height was determined. This study involved a Kansei assessment (SD method) based on five Kansei scores selected from a preliminary survey. The lever positions (height/horizontal distance) evaluated in this experiment were found to be suitable for vehicle designs under severe constraints. ANOVA analyzed the Kansei scores by gender and showed a statistically significant difference (P < 0.1). The results showed that places with good Kansei scores for females were mainly in the high Kansei area of males (average of 3.0 or more). Females' high Kansei score areas were smaller and located within the Kansei areas of males. Meanwhile, males' lowly evaluated (average value: -1 sigma or less) area was smaller and located within the Kansei areas of females. The relationship between subjects' height and Kansei were analyzed with linear and quadratic regressions. The distribution of the Kansei score on lever positions was graphically analyzed using LOESS nonlinear local regression. Acceptable lever positions were shown by LOESS. Finally, a statistical learning method, CART (Classification and Regression Tree) + Random Forest, was used to generate rule chains for the lever position specificity and anthropometric profiles. The results were in good agreement with the analyzed results obtained using traditional methods. To achieve safety in a collision accident and comfort at regular times in a narrow space of a vehicle interior, the parameters for lever positioning with respect to ease of operation were discussed for the findings in product development.
