Perceived Interior Space of Motor Vehicles based on Illusory Design Elements

Driver and passengers recognize the interior spaces of cars psychologically as well as physically. Since the car companies have difficulty extending the physical spaces of cars due to the cost and physical constraints, they tend to make an effort to widen the perceived space instead of the physical space. In this study, we aim to investigate the effectiveness of car interior designs to which optical illusions are applied to increase their perceived roominess. Instrument panels, door‐trim armrests, and A‐pillars were chosen as the interior spaces of cars that optical illusions were applied to because drivers most frequently recognize and use them. To get alternative car interior designs, the original car designs were modified by applying optical illusions. Also, the questionnaire that includes 28 questions was used to measure “perceived roominess,” “space completeness,” “openness,” “dullness,” and “narrowness” for original interior design and alternative designs based on optical illusions, and 30 people participated in the experiments that were conducted to compare among original and optical illusion–based designs. As a result, optical illusion–based designs were significantly better than original designs in terms of perceived roominess, and the following alternative designs were recommended: the instrument panel design of a 30% longer converging point than the original design, the horizontal door‐trim armrest design, and the A‐pillar design whose cross section is rectangular. We can conclude that the optical illusions can be applied to designing in‐vehicle spaces to increase perceived roominess.