Ever been stuck in traffic on a bus, wondering why is there legal street parking instead of a dedicated bus lane? A/B Street is a project to plan, simulate, and communicate visions for making cities friendlier to people walking, biking, and taking public transit. We create software to simulate traffic, edit streets and intersections, plan bike networks, create low-traffic neighborhoods, and educate the public about 15-minute neighborhoods through games. The project works anywhere in the world, thanks to OpenStreetMap. We amplify the efforts of individuals and advocacy groups who campaign to transition cities away from private motor vehicles. We believe in transparent and reproducible analysis, so all of our work is open source and based on public data. We believe everybody should have a voice in shaping their city, so our software aims to be easy to use.