In school choice systems, many families face geographic constraints. Yet, there is limited evidence on the association between school-based transportation and students' school choice, especially in fragmented transportation contexts. Using unique data on Detroit kindergarten students' eligibility and access to school-based transportation, we find that students with access to a bus at a school-- either a traditional or shuttle-style bus--were 4-5 percentage points more likely to enroll in that school. The association was greater for traditional buses in higher-crime neighborhoods and for shuttle-style buses for farther-away choices. We did not find that this association differed by block-group-level household car ownership. Our findings suggest that school-based transportation can increase school choice access, depending on policy design and contextual factors. [This report was written in collaboration with the Detroit Partnership for Education Equity & Research (Detroit PEER).]