In Singapore, 50 years is a long time and the train goes where you're going.

I'm not saying the US could pull off a Singapore, but there's no excuse for San Francisco, or LA, or any other large city to have done so.

We have highways everywhere... We could definitely dedicate the left most lane and convert every left most lane into people moving train tracks. Just because we haven't doesn't mean it isn't economical or feasible.