The biggest issue with bikes and walking in SF (as well as Seattle) is the hills. Oslo is relatively flat, as are other very bike centered cities like Amsterdam. Mind you, the rise of electric bikes is helping a lot, but it seems like hilly cities would only be able to get rid of cars if they replaced them with better, efficient, clean public transit. And it doesn't have to be just buses. Seattle, where they exist, escalators are very helpful. Maybe trams? I'm not a public trans expert by any means though. But as a guy who's not getting any younger, I definitely start to appreciate a hill escalator (there's a couple here in Seattle, some public, some parts of buildings) when my knees are hurting.