[ardecila]

I don’t know what kind of alignment gets a tunnel from Hoboken Terminal to Penn Station. If you wanna do that, realistically, you’d have to cross the river at something of a slant and build a north-south tunnel under 9th Ave or 10th Ave. But there would still need to be a 90-degree turn (below private property) right in the middle of the Hudson Yards skyscraper zone. I dunno how you build that without running into a forest of building foundations.

Would it be even possible to do a tunnel that literally ran north up the center of the Hudson River before turning east for a Penn Station approach? Might be cheaper than dealing with litigious neighbors on land, but a good regional rail system should actually have a stop in Chelsea instead of bypassing it with a long underwater segment.