This study compared two hypothetical transit scenarios with the current bus transit system for serving the transit passengers of Ann Arbor, Michigan, for a typical fall weekday in 2013. One scenario consists of an automated taxi system that allows only one rider at a time, and the other consists of a similar automated taxi system that allows ridesharing for up to four passengers. The two automated taxi scenarios were modeled on simulated transit passenger travel demand data via agent-based models. All three scenarios were then compared for their level of service, cost, greenhouse gas emissions, and congestion impacts. The automated shared-ride taxi transit service could provide a higher level of service at lower cost and lower carbon emissions than the current bus system. An automated taxi service without ridesharing would provide high levels of service at lower cost, but with higher levels of carbon emissions than the current bus system. Ridesharing is essential to obtaining the full cost savings and environmental benefits for an automated taxi system. Both automated taxi systems would likely increase peak-hour congestion by increasing peak-hour vehicle kilometers traveled.