|The proposed additions|
What is unclear is how this plan will connect with the Transbay Terminal, a project that is much more likely to move forward, since the previous Terminal has been demolished--buses are currently using a temporary structure. According to the Transbay Terminal project map (also below) on the website, the new Terminal will be bounded by Mission and Howard, and 2nd and Beale. So, far enough away from the black line on the above map that the central subway will not pass through the Transbay Terminal.
Additionally, the Transbay Terminal proposes building an underground right of way from King and 4th to the 2nd and Howard/Mission. This would serve as the SF terminus for high speed rail.
|"The rail line will be extended 1.3 miles underground from its current terminus at Fourth and King streets into the new Transbay Transit Center, providing a seamless connection between the Peninsula, the South Bay, Southern California and San Francisco’s Financial District."|
So to pull this together: HSR and Caltrains will come through the 4th and King station, and continue underground to the Transbay Terminal (blue line above). The 4th and King station will also have a branch northwest along 4th street, taking Muni light rail aboveground to Bryant, then underground to Chinatown.
I wonder how the underground subway would connect with existing Muni subway running along Market Street ... (update: commenter lmz informs that the Union Square Central Subway stop would have an underground ped connection to the Powell St station)
Also, can a high speed rail train execute a 90 degree turn? Maybe the right angle is an exaggeration of the publicity map; these are obviously not engineering specs, and it will be underground in any case (and thus not constrained by street grids).
Both of these projects are "actively searching for funding." Especially the central subway, which is more tenuous. If rail service is already being extended from 4th and King to 2nd and Mission, does it also need to go up to Chinatown along a separate route? Wouldn't it be better to extend, later, northward from the Transbay Terminal? I must be missing something here.