It can include mass transit too. For a practical example, 10km covers all of Was...

the_snooze 12 months ago | parent | context | favorite | on: 280M e-bikes and mopeds are cutting demand for oil...

It can include mass transit too. For a practical example, 10km covers all of Washington DC proper if you start at the center, nearly all of which is walkable/bikeable/transit-able.