Autonomous vehicle (AV) companies are now authorized to provide driverless ride-hailing services—known as robotaxis—in a growing number of U.S. cities. Despite rapid expansion, rich behavioral and attitudinal data on actual robotaxi use remain scarce, limiting researchers' and policymakers' ability to assess mobility impacts, monitor emerging risks, and guide safe scaling and efficient integration into the transportation system. This study examines robotaxi demand, impacts, safety perceptions, and public perspectives on complementary policies across four leading markets in the U.S.: Atlanta, GA; Austin, TX; Phoenix, AZ; and San Francisco, CA. Using a mixed-methods approach, the research team will conduct qualitative interviews with 20 robotaxi riders to surface motivations, evolving concerns, and unanticipated experiences, and deploy a survey to approximately 2,000 residents—riders and non-riders alike—across the four cities. Statistical analyses will address key questions: Who rides robotaxis, how often, and for what purposes? What motivates adoption over alternatives such as human-driven ride-hailing? How have riders adjusted their use of other travel options? How do safety perceptions vary across road user groups and real- world scenarios? Which policy options garner public support? This research will provide an important empirical benchmark, support more effective planning and regulatory decision-making, and contribute to a more informed and balanced public discourse on robotaxi deployment.