Autonomous vehicles are believed to be the next-generation technology for future societies. The energy and environmental impacts of autonomous vehicles have been realized to be important issues, but quantitative analysis is lacking. In this study, by using China's passenger vehicle fleet as an example, we evaluate the effects of autonomous vehicle deployment on greenhouse gas emissions in different scenarios of autonomous vehicle penetration rates and fuel consumption changes. A comprehensive literature review is conducted to support the study. Autonomous vehicles are found to potentially affect the total greenhouse gas emissions in multiple ways, including reducing vehicle ownership, increasing vehicle use intensity, and changing the vehicle fuel consumption rate. These impacts are mostly internally offset such that the overall impact of autonomous vehicle deployment on greenhouse gas emissions is not significant in the near-to mid-term. With a higher autonomous vehicle penetration rate achieved, in the optimistic scenario, a net reduction in greenhouse gas emissions is expected to be realized. In addition, the fuel economy levels of autonomous vehicles are highly uncertain and cause major uncertainties in the simulation results. More field tests and evidence are needed to improve the evaluation reliability.