Check out the map above pinpointing bicycle accidents around Boston. It was developed through a partnership of the Boston Area Research Initiative, the Boston Police Department and the Harvard School of Public Health (and it's got the imprimatur of Mayor Marty Walsh). From the research initiative: "[T]he database is based on BPD incident reports, and includes the original narratives with all identifying information removed, as well a variety of newly coded variables with other critical information such as, the time, place, weather conditions, and other factors that may have contributed to each collision." There's also data on whether the biker was wearing a helmet.
· BARI Releases Data on Bicycle Accidents in Boston [BARI]
· Our Fun with Cartography archive [Curbed Boston]