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Then came the gerrymander.
After the city decided not to rebuild the Embarcadero Freeway following the 1989 earthquake, Chinatown leaders began to view the Central Subway proposal as a form of payback that would bring commuters and shoppers into the heart of Chinatown, so shopkeepers would get back the business they believed was lost when the freeway came down. Union Square merchants, meanwhile, wanted to push the line a block west, so it could serve conventioneers who wanted to shop but didn't want to make the four-block walk from Moscone Center.
And so it was that in 1998 Willie Brown and his allies began to see the long-dormant Central Subway as less a planner's dream, and more an interest-group bargaining chip. The mayor successfully lobbied for Central Subway funds in Washington and Sacramento.
And at last week's meeting of the Third Street Rail Citizen's Advisory Group, where Muni officials unveiled detailed drawings of the proposed Central Subway, engineers described a tunnel that would make the difficult trip from the Mission and Third streets station to Stockton Street by curving to the right just before crossing Market, then making a 90-degree left turn west on Geary, then sharply doubling to the right in a "z" turn at Stockton, before heading north toward Clay Street.
Project engineers say this sharp zigzag would cause Muni trains to slow to a walking speed of 7 mph, creating routine, severe bottlenecks. If the Central Subway eventually forms the spine of a completed San Francisco rail transit network envisioned by planners, this bottleneck could potentially stall trains from the Richmond District to Visitacion Valley, and from North Beach to Ocean Beach. As a solution, engineers are considering straightening the zigzag by boring a hole deep into the earth underneath the Market Street BART tunnel. Engineers at last week's meeting refused to speculate how much more this deep dig would cost. (Because Kearny adjoins Third Street at a mild, 45-degree angle crossing Market, the previous design would have avoided these engineering problems altogether.)
There's another problem with the Stockton Street route: Because the lane is unusually narrow and lined with ancient, delicate buildings, engineers face a difficult challenge designing a Clay Street entrance that allows for aboveground pedestrian and auto traffic, while leaving historic buildings unharmed.
Consulting engineers will spend the next few months conducting preliminary design studies that will reveal exactly how daunting or expensive the current design may or may not be. This raises the question: If the Stockton Street design proves too costly or impractical, will planners reconsider the old Kearny Street design? They will not, says Sue Olive, manager for the Third Street light-rail project.
The political decision to run the tunnel up Stockton Street has already been made, she says, and engineers will design around it.
It was a different sort of interest-group battle that shaped the Central Subway gerrymander's southern tail. As with the line's northern snout, understanding the southern gerrymander requires a bit of history – but this time, it's bureaucratic history.
Over many years, Muni and the Department of Parking and Traffic fought block-by-block battles over whether to facilitate the flow of transit vehicles or cars. The city's charter requires that transit receive preference, but the DPT's traffic engineers, trained in the art of increasing the number of cars per minute flowing along streets, resisted. This friction created repeated jurisdictional battles involving Muni, the DPT, the Planning Department, the Redevelopment Agency, the Department of Public Works, and other agencies. As a result of Proposition E, passed in 1999, Muni and the DPT were merged last summer under a new Municipal Transportation Authority, promising a new era of transit harmony. But old war wounds remain, one of them being a bizarre split of the Central Subway system into two separate north- and southbound lines, one-fifth of a mile apart.
Heading south from the proposed Third and Mission streets station, the Central Subway tunnel would split at Harrison Street, with the southbound tunnel veering west to Fourth Street. The two, separated tunnels would emerge onto street level between Bryant and Brannan streets, and continue to King Street. The southbound line would stop near the Caltrain station on Fourth Street. The northbound line would stop 400 yards away in front of the Giants' ballpark.
Project engineer John Thomas told me the split-track design will preserve current automobile traffic patterns on Third and Fourth streets, which he described as "important arteries."
Thomas acknowledged that having a quarter-mile of busy streets separating two halves of the southern station at King Street will likely create passenger confusion. Splitting the tunnel 400 yards apart will add about 5 percent to the project's cost, or about $30 million, give or take a few million, he said. And to bring the two lines together so they can continue south toward the Bayview, this automobile-friendly compromise design calls for a horridly slow series of 90-degree "z" turns that, like the zigzag at Stockton and Market, will create transit-rage-inducing commuter bottlenecks.
Putting north- and southbound lines in a single Third and King streets station would eliminate confusion. Running the line one block down the middle of Third Street, with traffic traveling in the same direction as train cars on either side, would result in a system faster, cheaper, more efficient, and easier to understand than the current design. But it might hinder automobile traffic.
Critics describe the trade-off as absurd. Spending tens of millions of dollars to preserve automobile traffic flow as part of a project created specifically to reduce traffic flow is preposterous, they say. And the split station isn't just confusing; it's downright dangerous.
