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“We know what we need to do. He mentioned the subway’s aging signal system. We live in a digital age. Our signal system isn’t even analog. It’s mechanical.”

by gdubs 9y ago

“We know what we need to do. He mentioned the subway’s aging signal system. We live in a digital age. Our signal system isn’t even analog. It’s mechanical.” Now there's something I'd like to read a HN post on.

adammck 9y ago
You might find this interesting: https://www.theatlantic.com/technology/archive/2015/11/why-dont-we-know-where-all-the-trains-are/415152/ https://www.theatlantic.com/technology/archive/2015/11/why-d...
madamelic 9y ago
What Adam (?) said, but now in video form: https://www.youtube.com/watch?v=Mjx3S3UjmnA https://www.youtube.com/watch?v=Mjx3S3UjmnA
dajt 9y ago
Look up mechanical signal interlocking. It's pretty interesting.
Gibbon1 9y ago
Reminds me of an article I read on some guys that updated the controls for a sewage tunnel that runs under the Hudson river. The more they investigated the dynamics of a 1000 foot long, 10 diameter pipe full of poo, the more terrified they became. And more impressed with the long dead engineers that originally solved the problem in the 1920's. Original controls were all mechanical.
crocal 9y ago
It's actually partially true. The NYCT signalling system is more like a sandwich. At the bottom they have a legacy system called AWS. It is built using a logic of relays that will raise or lower mechanical arms on the tracks. When the arm is raised it will collide with a valve on the train that, once opened will apply the brakes on the train forcibly. The logic driving this is from the beginning of the 20th century and seriously pretty clever. The guys at the time even timed the relays to raise arms according to the recommended maximum speed for driving the train. On top of this, computer based systems have been deployed, especially CBTC, starting in the Canarsie line. So, frankly, the statement made is quite inaccurate. The system works in the sense that it allows higher potential capacity. The real problem is that with a legacy sandwich so deep the failure rate is terrible, especially when age of material and obsolescence kicks in. Now imagine fixing a technical debt that spans nearly 2 centuries, with limited maintenance time, and life critical functions buried inside. This is the problem.

by gdubs 9y ago

adammck 9y ago

You might find this interesting: https://www.theatlantic.com/technology/archive/2015/11/why-dont-we-know-where-all-the-trains-are/415152/ https://www.theatlantic.com/technology/archive/2015/11/why-d...

madamelic 9y ago

What Adam (?) said, but now in video form: https://www.youtube.com/watch?v=Mjx3S3UjmnA https://www.youtube.com/watch?v=Mjx3S3UjmnA

dajt 9y ago

Look up mechanical signal interlocking. It's pretty interesting.

Gibbon1 9y ago

Reminds me of an article I read on some guys that updated the controls for a sewage tunnel that runs under the Hudson river. The more they investigated the dynamics of a 1000 foot long, 10 diameter pipe full of poo, the more terrified they became. And more impressed with the long dead engineers that originally solved the problem in the 1920's. Original controls were all mechanical.

crocal 9y ago

It's actually partially true. The NYCT signalling system is more like a sandwich. At the bottom they have a legacy system called AWS. It is built using a logic of relays that will raise or lower mechanical arms on the tracks. When the arm is raised it will collide with a valve on the train that, once opened will apply the brakes on the train forcibly. The logic driving this is from the beginning of the 20th century and seriously pretty clever. The guys at the time even timed the relays to raise arms according to the recommended maximum speed for driving the train. On top of this, computer based systems have been deployed, especially CBTC, starting in the Canarsie line. So, frankly, the statement made is quite inaccurate. The system works in the sense that it allows higher potential capacity. The real problem is that with a legacy sandwich so deep the failure rate is terrible, especially when age of material and obsolescence kicks in. Now imagine fixing a technical debt that spans nearly 2 centuries, with limited maintenance time, and life critical functions buried inside. This is the problem.