alt Hacker News> If you have enough density to support a bus lane, you have enough density to support a subway.
Not at all. Building a subway in most US cities right now is very expensive. Raising the tax revenue alone is probably a non-starter.
Moreover you're going to have to close the road down anyway to do any form of cut-and-cover or even deep bore construction, which means every business on the corridor and every person who lives on it is going to get angry for as long as the subway is being built.
There's no painless way to do infill public transport. The problem is that nobody in the US is willing to compromise.
> Building a subway in most US cities right now is very expensive.
This is true but seems like a problem worth solving. It's also true of more than subways; we have the same problem with bridges, housing and many other things. Better to get on with fixing it than use it as an excuse for doing something worse.
> Moreover you're going to have to close the road down anyway
That's a one-time cost, and you're not required to close a 500 mile stretch of road for years on end. Dig one block, install the tunnel, cover it, dig the next block.