This map is built on top of BlakeRobMills’s map which can be found on Twitter and on GitHub.
I merely added the data and the visualization for Zurich, Switzerland, changed the layout and some of the styling, added an R project, hopefully improved some of the code (the original R code didn’t load all necessary libraries, e.g.) and expanded the comments a bit. Kudos go to BlakeRobMills for the idea and original execution.
Update: I corrected the "London" data to show cycling infrastructure in London, UK, instead of London, Ontario, Canada.