A hallmark of Vision Zero, the multinational policy platform to eliminate traffic deaths, is its emphasis on numbers. Austin, San Francisco, Los Angeles, and many other cities describe how they target corridors for safer street engineering, driver education, speed limit reductions and other interventions with the phrase “data-driven.”
The problem is that the data driving such efforts are rarely, if ever, complete. Most cities rely on local police to record car crashes, including those involving pedestrians and cyclists who are often the focus of Vision Zero programs. But sometimes police officers are never called or never show up. Those involved in a crash may leave rather than waiting for authorities arrive, or they might refuse assistance. That leaves gaps in official knowledge of where traffic dangers lie, which inform Vision Zero efforts to fix them.
