Transbay Terminal Rail alignment development

• Overview of terminal geometrical constraints
  
  
• Overview of entire extension alignments (1.9mb PDF) (background image)
  
  
• Handout briefly summarizing some of the trade-offs of accepting different constraints in track and platform geometry and suggesting some desiderata for any downtown San Francisco railway station.
  
  
• Oblique orientation (aka "Richard Preferred Alternative" -- in February 2001, but subsequently considerably refined).
  
  • Through platforms 360m, 360m, 370m, 370m, 330m; Stub platforms: 310m, 310m.
    Nearly straight platforms. Western approach from Second Street, eastern under Mission. 180m minimum radius. 500m/800m platform curvatures.
    Requires purchase of 301 Mission (3719-1, 3719-17). Baywards continuation under Mission Street, under Muni Metro Turnback and into the Bay. Fantasyland!
  • As above, but with four stubs: 300m, 270m, 260m, 240m.
  • As above, but with no stubs. Through 360m, 360m, 370m, 380m, 380m.
  • Western approach from Essex Street, eastern under Mission. 180m minimum radius. 500m/800m platform curvatures.
    Through platforms 290m, 290m, 310m, 310m, 310m.
  • As above (Essex/Mission) but with 150m curves. Through platforms 290m, 290m, 310m, 300m, 310m.
  • As above (Essex/Mission 150m) but with a sixth, terminating. road at the cost of extra private easements.
    Through platforms 290m, 290m, 310m, 300m, 310m, 310m.
  • Just for reference. 301 Mission avoided, but at large cost. Straight (or nearly so: 800m radius) stub platforms. 180m minimum radius.
    Stub platforms: 280m, 280m (possibly through), 320m, 320m, 310m.
• Platforms built on a 500m curve, minimum radius 180m (ie UIC compliant!). Second Street.
  
  • The (non-oblique) winner so far: 6 through platforms: 290m, 320m, 360m, 340m, 340m, 330m
• What happens when mimimum radius is increased to 200m, and when platforms are not allowed to be curved. For edification only, as the trade-offs make these poor contenders.
  • 200m min radius, 500m platform radius. 5 through platforms: 280m, 300m, 300m, 270m, 270m
  • 200m min radius, straight platforms. 4 through platforms: 180m, 180m, 200m, 200m. Two terminating: 250m, 230m
  • 200m min radius, straight platforms. 5 through platforms: 180m, 180m, 180m, 190m, 190m
• Much older concepts with 150m minimum radius.
  
  • Platforms built on a 500m curve, trading CCTV monitoring of invisible train doors for longer platforms and smaller takings.
    Western approach from Second Street, eastern from Main.
    150m minimum radius. Only 100m or so of straight platform.
    • 6 through platforms: 300m, 360m, 360m, 380m, 390m, 390m
    • 5 through platforms: 360m, 360m, 380m, 390m, 390m
  • As above, but curved at the western end only; losing 30m of overall platform length in order to have 150m of straight platform.
    • 6 through platforms: 285m, 295m, 340m, 365m, 365m, 365m. One optional stub platform of 240m.
  • Straight platforms. Western approach from Second Street, eastern from Main. 150m minimum radius.
    • 6 300m through platforms.
  • Straight platforms. Western approach from Essex Street, eastern from Main. 150m minimum radius.
    • 5 200m through platforms, 1 230m stub.
• PTG Madness.
  • 150m curvature, straight platforms, approaches from Second and Main streets.
    This is the basis for "Option 2" in the TTT EIR NOP.
    Yes, this is seriously what they've drawn up and are proposing. Imagine trying to actually operate trains in and out of this! Conflict-o-rama!
    Stubs 320m, 260m, 260m, 290m. Through 290m, 290m
    Note that these aren't the actual Super Secret Engineering Drawings: they're my reconstructions, but are very close to the original.
    Extended Dance Remix showing throat nuttiness extending unusable triple trackage to Bryant Street.
  • Ugh! This is the basis for "Option 1" in the TTT EIR NOP.
    The reality is actually far, far, far worse than I imagined here. What I've drawn (with its masses of approach special work and resulting availablility of three simultaneous approach paths to most possible platform combinations) might actually be operable, the real PTG Madness is absolutely untenable.
    Of course, this is all academic, since there is no way to construct this mess, given the depth of the tracks (under a mandatory mezzanine, circa 30 feet below sea level) and the height of the terrain (over 80 feet above sea level where the junction would be located), all combined with poor rock (entered around Folsom Street) and the overlying bus ramp and Fremont Street bridge ramp.
    Extended Dance Remix showing nutty junction and putative transbay alignment.