Is microtransit a cost-effective alternative or a costly competitor to public transit?

Many transit agencies have piloted or introduced on-demand, flexible, and door-to-door microtransit services, seeking ways to attract new riders and bridge first- and last-mile gaps to existing fixed-route transit services. Microtransit services may affect an agency's fixed-route ridership, and may also add more costs — in budget, staff resources, and potentially shifted ridership. It is unclear to what extent agencies explicitly design their microtransit programs to meet their transit ridership goals, or how microtransit affects transit ridership in practice. In this paper, we fill this gap by answering three related questions: 1) To what extent is increasing public transit ridership a goal of microtransit programs? 2) Do microtransit evaluations measure programs' impacts on public transit ridership, and if so, how? And 3) Under what conditions do microtransit programs boost or cannibalize public transit ridership? To answer these questions, we first analyze whether and how 17 microtransit pilot evaluations from across the U.S. define and measure ridership impacts. We then examine telematics and rider survey data from four microtransit programs in California's Clean Mobility Pilot program, alongside local public transit route, budget, and ridership data. We find that while many agencies identify microtransit ridership goals, they varyingly measure ridership effects. Few microtransit services appear to increase overall transit ridership, and some services provide a more reliable alternative or operate outside fixed-routes. Our findings suggest that transit agencies can improve transit ridership and connectivity more systematically if they design microtransit programs to fill spatial and temporal gaps in fixed-route service.