Development of a predictive model and design guidelines based on subjective evaluation of rear seat passenger headroom

Abstract

A laboratory study of rear-seat passenger headroom perception was conducted with 102 men and women using a reconfigurable vehicle mockup. The subjects rated three different roof shapes at five different roof positions on numerical sufficiency and acceptability scales. The subjects’ head and hair contours were digitized prior to testing and combined with measured head positions in the vehicle mockup to obtain actual head and hair clearance dimensions in each of the test conditions. Statistical analysis demonstrated that subject body dimension (stature), vertical roof position, lateral roof position, and vertical roof-to-rail offset all have important interactive effects on headroom perception. For example, the degradation in perceived headroom with an inboard lateral movement of the roof rail is dependent on the vertical offset of the rail relative to the roof. Logistic regression analysis was used to create statistical models that accurately predict the percentage of an occupant population who will rate the headroom at a desired criterion level as a function of roof geometry and position. Three new geometric measurements are introduced that are substantially better related to subjective headroom perception than the conventional SAE dimensions. In addition to the mathematical models, which can be applied to any desired population, an Appendix is provided with graphical plots that can be used as a design guide for one particular reference population.