Connected and automated vehicles (CAVs) are expected to lead to increased capacity and reduced accidents andpollution. Regarding the connected automated transport systems (CATS), shuttle bus services are expected to be the first to align with their large-scale business cases increasing urban transport activities. This study aims to examine the impacts of autonomous transit services on traffic, environment and safety in an urban environment, through several use cases and scenarios executed on a microsimulation testbed network. Three different autonomous public transit services were implemented and the simulation scenarios differed in terms of CAV market penetration rate, traffic conditions and service operation. Point-to-point shuttle bus service operation in a small-scale network led to increased delays and driven kilometers, while operations in a large-scale network did not show significant differences. On-demand shuttle service showed decreased delays and kept constant the driven kilometers. The existence of dedicated lanes did not affect traffic.