The goal of reducing or eliminating traffic fatalities and severe injuries in cities requires new and openly accessible tools that can be used and shared by community groups, agencies, and activists alike. Crash Data Explorer is an open source analysis and engagement tool for urban pedestrian and bike safety. It is a fast client-side javascript web application leveraging Leaflet, Chart.js, and CitySDK. Its main setup requirement is for traffic crash and boundary data to be converted into specified GeoJSON formats. Sample Python scripts which do this for Columbus Ohio’s crash data and geographies are provided with the source code.