The Tappan Zee Bridge is about to fall down. As a result, the replacement and widening project is in spare-no-expense mode. Ordinarily, widening a bridge from seven lanes to ten would be judged in terms of costs and benefits, after which the costs would be ignored as they always are for US road projects. But now everyone thinks New York needs this project, to the point that even transit and livable streets advocates are more worried about commuter rail tracks on the new bridge than about the costs of the entire project.
Cap’n Transit cribbed study numbers before they disappeared from the official website. The budget of the project, without the transit component, was about $7 billion, and is now up to $8.3 billion; this includes highway widenings at both ends. The transit component people are fretting about is another $1 billion for BRT and $6.7 billion for commuter rail.
To put things in perspective, consider the Øresund Bridge-Tunnel complex. Whereas the Tappan Zee is 5 kilometers of bridge, Øresund consists of 8 kilometers of bridge, an artificial island with 4 additional kilometers of road, and 4 kilometers of tunnel. The cost, including landworks on both sides, was a little more than €3 billion in 2000, which works out to $5.5 billion in 2010. The bridge-tunnel is narrower than the Tappan Zee replacement – four lanes of traffic plus two tracks of rail – but it’s also three times as long, and more complex because of the tunnel.
More importantly, if the Tappan Zee really needs that capacity, and width is such a constraint, they should build rail first, BRT second, and car lanes last. Roads will never beat mass transit on capacity per unit width of right-of-way. With all traffic from Rockland to Westchester County funneled through one chokepoint, and some centralization of employment (in Manhattan, White Plains, and Tarrytown), rail could work if it were given the chance. So the only environment in which a bridge with so many traffic lanes is justified is one in which the cost of ten lanes is not much more than the cost of four.
To be completely fair to irate Rockland County residents, more people use the Tappan Zee than Øresund, since the tolls are lower and it’s a commuter route. But not enough. The bridge is crossed by 138,000 vehicles per day. This means the replacement and widening project, excluding all transit improvements, is $60,000 per car. With normal commuter seat occupancy, it’s perhaps $50,000 per person. Transit projects in the US routinely go over this, but those are for the most part very low-ridership commuter rail projects. Second Avenue Subway, the most expensive urban subway in the world per kilometer, is about $25,000 per expected weekday rider.
Given the high cost, the only correct response is a true no-build: dismantle the bridge, and tell people to ride ferries or live on the same side of the Hudson as their workplace. Given expected ridership and Øresund costs, I believe the Tappan Zee replacement would make sense at $3 billion, with the transit components; without, make it a flat $2 billion. Go much above it and it’s just too cost-ineffective. Not all travel justifies a fixed link at any cost.