[addicted]

If you’re digging an underground tunnel in NYC throwing low throughout roads in it is the worst idea possible.

There is absolutely no reason to not put a subway track, which would have an order of magnitude higher capacity, in an underground tunnel instead.

[clairity]

you could also put in a subway track down the middle while you're at it, but the primary point of undergrounding the road is so we get our most precious above ground space back for people, not cars. it's not simply about optimizing throughput, though that's also a worthy, and compatible, goal.