Pittsburgh’s North Shore Connector is quite the opposite. Pittsburgh’s entire structure is divided by two rivers. Local light rail service crosses one of them but not the other. Connecting to the North Shore will suck up vast numbers of auto drivers because the chokepoint in that area was the bridges which are about to be paralleled by tunnels. It serves both people coming from the north, who will park (at *privately built* parking garages) before crossing the bridges, and people coming from the south and east to the major attractions on the North Shore.

BRT? For a high-volume application, that’s a joke. It costs twice as much to operate every year as light rail and carries fewer people. Exhibit A: Pittsburgh’s busways!

Surface LRT? Across a RIVER? Starting from underground in the most expensive part of town? The light rail is already underground downtown, it has to either bridge or tunnel to cross the river, and for once the tunnel would be cheaper and more effective (lower operating costs, faster service) than a new bridge, thanks to the existing structure.

They knew what they were doing with the alternatives analysis on this one. If the existing light rail hadn’t been run underground back in 1981, a different scheme might have made sense, but with it already in a cut-and-cover tunnel through downtown Pittsburgh, pulling it to the surface at steep grades in order to run it across a new bridge over a wide river (the Alleghany) river would have cost more than the bored tunnels. A backtracking route reusing the unused lower deck of the Fort Wayne Railway Bridge might have worked, but the deck was too deteriorated.

The line comes to the surface as fast as possible on the North Shore. It’s really only underground because of the river and the existing downtown structure. When finished Pittsburgh will have a “T-shaped” grade-separated core light rail network, at the surface on all three ends and pointing outward in the three logical directions for extension. But the short, expensive subway connection had to be built before the future, cheaper surface extensions can be built.

The fact that it will have substantial immediate benefits even as a short stub line makes it even more sensible.

They’re not building tunnels just to be cool.