|Transbay: courtesy of Pelli Clarke Pelli.|
During the discussion at the Metropolitan Transportation Commission over how to allocate Bay Area transportation stimulus funds, MTC proposed applying for $195-$400 million of funds to build the train box at the Transbay Transit Center in San Francisco. This money would come from the $8 billion of high-speed rail grant money that was ultimately integrated into the final stimulus bill. Then, the California High-Speed Rail Authority made public its concerns that the Transbay Transit Center, as currently designed, would be inadequate to satisfy its new needs for 12 trains per hour, increased from six trains, for each of the six peak hours everyday. Under the current plan for the Transbay station, tracks would transition underground west of 4th Street, leading to a new subway station at 4th and Townsend, where Caltrain currently terminates. A three track tunnel would then curve off Townsend and north onto 2nd Street, turning once more and splaying out to a six track throat leading to the Transbay underground rail station. The station had been planned to include three island platforms and six platform tracks: two tracks for Caltrain, and four for high-speed rail. According to ridership projections, 2030 Transbay ridership for Caltrain might be 31,500 and 4th/King Caltrain ridership at 17,100. Daily high-speed rail ridership at Transbay by 2030 was projected to be in the vicinity of 26,500.
The basic problem is a perceived discrepancy between the CHSRA’s ridership projections and an as-yet unrevealed operational plan that would require 12 trains per hour and 8-10 platform tracks, rather than four. The Transbay Joint Powers Authority will need a detailed explanation from CHSRA justifying its demand for extra capacity. But what would it take to build more tracks? To avoid the cost of additional right of way acquisition, the TJPA considered a design which would accommodate six additional tracks for high-speed rail on a third level underneath the currently planned platform level. (The above image depicts the concourse mezzanine and the single planned platform level.) The extra cost of such a change would be at least $1 billion: $500 million for the expanded train box and $500 million extra for the actual rail extension — and that even lowballs it, because it assumes early construction of the expanded train box. Is there a demonstrated need for the extra capacity, that would justify somehow scraping together even more funding for Transbay? In Tokyo, 13 trains per hour at peak time for the Tokyo-Osaka Shinkansen line use just six platform tracks. But that’s for a line that carries 145 million passengers, which exceeds CHSRA’s projections even at full-system buildout — and that’s in a country whose current population is at least double California’s projected population by the year 2050. The TJPA also considered a worst-case scenario with a higher Transbay ridership (12.7 million annual riders), in which an especially large number of passengers happened to concentrate on peak hour trips. But even in that worst-case scenario, combining the CHSRA’s ridership projections with its new alleged need for increased peak capacity, the trains would only be 12-43% full at the newly increased service levels. Note that there are still other design options that were once considered — including tail tracks and an underground track loop — which would improve the flow of trains in and out of the station. And in the long, long, term, beyond 2030? An additional tube under the Bay has long been discussed in hushed tones, even though it is not yet being planned outright. If an additional tube contained four tracks (with two broad gauge tracks for BART, and two standard gauge tracks for intercity and high-speed rail), it would dramatically increase pinched transbay capacity. It would open up new possibilities for regional connectivity, and it would finally integrate Oakland and the East Bay directly into the state’s high-speed rail network. It would also mean that trains would run through Transbay, rather than terminating there, which would put less stress on that station.