This horizon scan provided a comprehensive survey of technology, economic, and planning trends for cities participating in the Bloomberg-Aspen Initiative on Cities and Autonomous Vehicles. Written as a general purpose primer outside transportation policy circles, it framed basic questions with support from visual storytelling through charts and figures. Key orienting questions we addressed include: When will autonomous vehicles arrive in significant numbers? What types will take off first? Where will the hotspots of AV use be? Who are the key players in this new industry and what do they want from cities? How can cities assess the risks and opportunities and act strategically to maximize the potential benefits and minimize negative impacts?