I think the original idea behind the suburb is that you don't have to interact with anyone you don't want to interact with. A much nicer way of saying that is t

I think the original idea behind the suburb is that you don't have to interact with anyone you don't want to interact with. A much nicer way of saying that is they are more efficient. Or at least that was the original intention. The layout of the subdivision is that maximizes the lawn space you get, for the amount of routing (e.g. traffic intersections) to whatever your destination was. And since driving is nominally the fastest way to get somewhere, the suburbs were how you were going to do it. It's like someone decided on the efficiency goal, and looked at what was the fastest means of transport, and derived from there. Maybe you could say there might've been some redlining too – just put the folks you don't want to interact with in that subdivision over there –, but in all, the problem is that it ultimately becomes: only efficient at one thing, and that's getting to work and back home. And it got terrible even just for that because cars as a means of transport doesn't scale well with population. Then public transit becomes a hack to try to make it work. In the Bay Area and DC, you have highly efficient transit systems that are good for getting to downtown, and pretty much terrible at most other things. In both places, you still need cars for the last mile, when you're leaving "downtown." In the Bay Area, only the Mission District is truly walkable, of all the non-downtown neighborhoods it connects. So now there's car sharing at most of the BART stations. But at least we have them. Not sure if there are any for the Caltrain.