5 ms·

That is fascinating, thanks for sharing. I had no idea the NYC subway was being run by a 100 year old electro-mechanical system.

hga 11y ago
The D.C. Metro system was planed in the '60 and constructed in the '70s, with the first operations starting in 1976. It too is based on electro-mechanical relays, although it's more ambitious, after the operator closes the doors and sees all is fine, he hits a "go" button and the system automatically takes the train to the next station, avoiding collisions as long as the "is there a train in the next segment" sensor system is working.
- JonathonW 11y ago
  The DC Metro actually (mostly) hasn't used their automatic train control system in full automatic mode since a collision in 2009 that killed nine (for which the ATC system was directly responsible; a faulty circuit both forced a train to stop and rendered it invisible to the control system). Safe train control seems like it needs a little more sophistication than '60s or '70s tech was able to give. For one, it's common sense that a train that disappears from the system isn't really gone-- but the Metro system couldn't take that into account. Stuff like that should be pretty trivial today.
  - AnthonyMouse 11y ago
    > For one, it's common sense that a train that disappears from the system isn't really gone-- but the Metro system couldn't take that into account. Stuff like that should be pretty trivial today. It was pretty trivial in the 1970s. Require the sensor for an adjacent segment to be engaged before the sensor for an active segment will disengage. You can't do any computation with modern computers that you couldn't have done with relays in the 1970s, or the 1870s for that matter. Mechanical relays are slower, less reliable and more expensive than transistors... but they do the same thing.
  - Symbiote 11y ago
    The Victoria Line was the first automatic railway, opening in 1968. There have been no accidents. The system was replaced a couple of years ago with a new one, to allow an even higher frequency of service. https://en.m.wikipedia.org/wiki/Victoria_line https://en.m.wikipedia.org/wiki/Victoria_line

hga 11y ago

The D.C. Metro system was planed in the '60 and constructed in the '70s, with the first operations starting in 1976. It too is based on electro-mechanical relays, although it's more ambitious, after the operator closes the doors and sees all is fine, he hits a "go" button and the system automatically takes the train to the next station, avoiding collisions as long as the "is there a train in the next segment" sensor system is working.

JonathonW 11y ago
The DC Metro actually (mostly) hasn't used their automatic train control system in full automatic mode since a collision in 2009 that killed nine (for which the ATC system was directly responsible; a faulty circuit both forced a train to stop and rendered it invisible to the control system). Safe train control seems like it needs a little more sophistication than '60s or '70s tech was able to give. For one, it's common sense that a train that disappears from the system isn't really gone-- but the Metro system couldn't take that into account. Stuff like that should be pretty trivial today.
- AnthonyMouse 11y ago
  > For one, it's common sense that a train that disappears from the system isn't really gone-- but the Metro system couldn't take that into account. Stuff like that should be pretty trivial today. It was pretty trivial in the 1970s. Require the sensor for an adjacent segment to be engaged before the sensor for an active segment will disengage. You can't do any computation with modern computers that you couldn't have done with relays in the 1970s, or the 1870s for that matter. Mechanical relays are slower, less reliable and more expensive than transistors... but they do the same thing.
- Symbiote 11y ago
  The Victoria Line was the first automatic railway, opening in 1968. There have been no accidents. The system was replaced a couple of years ago with a new one, to allow an even higher frequency of service. https://en.m.wikipedia.org/wiki/Victoria_line https://en.m.wikipedia.org/wiki/Victoria_line