Shared automated vehicles (SAVs) in the form of low-speed driverless shuttles have the potential to improve independent mobility for older adults and people with disabilities. At full vehicle autonomy and in the absence of an onboard operator, tasks such as ingress-egress, interior circulation, and securement of passengers and carry-on items will need to be safe, efficient, and independent. This paper describes a novel laboratory apparatus for conducting inclusive design research related to SAVs and presents preliminary findings from an ongoing preliminary study examining the effects of interior design configuration on ingress-egress performance for six wheelchair users. Early findings emphasize the interactions between diverse user abilities and technology design on user performance. The study demonstrates the potential benefit of full-scale physical simulations to investigating a broad range of usability and inclusive design issues related to emerging SAVs.