How can open-source software and algorithms accelerate the green transition of European cities? Today, urban cycling infrastructure is often planned ad hoc, on little evidence, and outsourced to costly consultancies. Algorithms can turn that into an empirical, automated process – and when they're open-source and user-friendly, they become reproducible, transparent, and open even to citizen science. This session presents BikeNetKit (https://bikenetkit.org), a suite built over seven years of research, to show how open tools can close the gap between sustainable planning and real policy making.