[hk2001]

Tokyo is hyperdense despite its massive size. I think the point is less "what percentage of the city can I reach easily on a bike" and more "how many places of interest can I reach easily on a bike". In metropolises in Europe or Japan, 5km contains a lot. In the lower density, sprawling cities of North America, there isn't nearly as much utility to the places you can travel to within 5km.