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In order to support a line running 24/7, you have to build a lot of bits and pieces to include more redundancy. For example, the two miles of Second Avenue Subw

In order to support a line running 24/7, you have to build a lot of bits and pieces to include more redundancy. For example, the two miles of Second Avenue Subway has three crossovers, all of which need multiple switches, so that trains can run on either track, allowing maintenance crews to cut power and safely work on the train lines during more quiet hours of the day with minimal disruption. Conversely, BART in San Francisco has very few crossovers. That was cheaper, as signalling and switch infrastructure is expensive, but also makes it much less granular, and as such, harder to do any sort of maintenance.

pas 10y ago
Tunnel boring, digging and other soil/earth works are the big cost factors, the required logistics, and regulatory processes (permits, permits and making sure that you have a plan when you close important lanes on streets and avenues of a big and busy city - so traffic engineering). The crossovers probably cost so much because they're underground and require extra tunnel space. (They require extra (as in between the two-or-more tracks that are being switched) foundations above ground too, which is probably more expensive than the switch itself.) However, I'd like to see a cost breakdown.
rtpg 10y ago
So are subway lines switching over constantly in NYC? Or is the redundancy all over? That sounds like a high price to pay for 24/7 service. Even the busiest lines in Tokyo are mostly single-rail. Of course, when a train breaks down, then nothing can happen, but at least you don't need 4 sets of rails, only 2 (one for each direction). There's probably way less in terms of delays because of that too. Each train is on its own set of tracks, so little cross-cutting.
- bogomipz 10y ago
  >"Even the busiest lines in Tokyo are mostly single-rail." But aren't most of the train lines in Tokyo owned and operated by separate competing companies They don't have to interoperate or not that much correct? Once upon a time the trains in New York City were also owned by separate competing companies, there was the IND, BMT, and the IRT but they now operate as one entity under the MTA. As a result all these lines were originally built differently with different tunnel widths and platform to accommodate the different size cars. I think this level of interop adds to the complexity of the system as a whole.

pas 10y ago

Tunnel boring, digging and other soil/earth works are the big cost factors, the required logistics, and regulatory processes (permits, permits and making sure that you have a plan when you close important lanes on streets and avenues of a big and busy city - so traffic engineering). The crossovers probably cost so much because they're underground and require extra tunnel space. (They require extra (as in between the two-or-more tracks that are being switched) foundations above ground too, which is probably more expensive than the switch itself.) However, I'd like to see a cost breakdown.

rtpg 10y ago

So are subway lines switching over constantly in NYC? Or is the redundancy all over? That sounds like a high price to pay for 24/7 service. Even the busiest lines in Tokyo are mostly single-rail. Of course, when a train breaks down, then nothing can happen, but at least you don't need 4 sets of rails, only 2 (one for each direction). There's probably way less in terms of delays because of that too. Each train is on its own set of tracks, so little cross-cutting.

bogomipz 10y ago
>"Even the busiest lines in Tokyo are mostly single-rail." But aren't most of the train lines in Tokyo owned and operated by separate competing companies They don't have to interoperate or not that much correct? Once upon a time the trains in New York City were also owned by separate competing companies, there was the IND, BMT, and the IRT but they now operate as one entity under the MTA. As a result all these lines were originally built differently with different tunnel widths and platform to accommodate the different size cars. I think this level of interop adds to the complexity of the system as a whole.