Metro has no plans for ATC as 10th anniversary of deadly accident approaches

[davinp]

This weekend marks 10 years since two Metro trains collided on the Red Line between Fort Totten and Takoma after the automatic train control system failed. Nine people died, and the system has been operated manually ever since. Transportation Reporter Adam Tuss reports the agency is not in any rush to return to automated operation.

https://www.nbcwashington.com/traffic/t ... 40682.html

You know, if Metro wasn't using the 1000 series, the accident may not have been as deadly. Metro knew those 1000 series cars could telescope as was seen in previous collisions but continued to use them anyways. They weren't fully retired until 2016, but should have retired much sooner

[JDC]

I do not believe this is correct (and I think you're referring to ATO; I do not believe ATC was ever disabled). My understanding is that Metro is planning ATO return this summer.

[danib62]

They are only bringing back automatic doors for now.

[davinp]

I do not believe this is correct (and I think you're referring to ATO; I do not believe ATC was ever disabled). My understanding is that Metro is planning ATO return this summer.

I think I got confused between Automatic Train Control and Automatic Mode or Automatic Train Operation

[Head-end View]

I've been away from this thread for a while and I'm a little confused. As I understood it the collision happened because a track circuit failed, and did not detect a train, causing the following train to receive a false clear indication. Seems to me the same collision would have happened even in manual operation. So why is WMATA afraid to run trains in automatic mode if that's not what caused the incident? Please correct me if my understanding is a little off.

[dcmike]

You are 100% correct, and are asking the $64,000 question that all the local media have failed to.

My internal contacts are tight-lipped about this, but I have a (two part) theory about this:

a) there are an increasingly large number of bobbing track circuits around the system and there has been for some time; when a train in ATO encounters theses areas, it will drop out of auto.
b) none of our current fleets have ever demonstrated consistent precision 8-car stops, recall that when we did run in auto previously all stops were center platform and 8-car trains were run in manual.. the 2/3/5/6k with Alstom-based carborne ATC is fatally flawed in that it doesn't use an accelerometer to guide station stopping profiles and therefore has never worked correctly.. it is my understanding that Ansaldo, supplier of 7K ATC equipment, has yet to deliver an accepted solution either, 7Ks in testing tend to stop short or overrun more often then hit the target.

[Sand Box John]

dcmike
b) none of our current fleets have ever demonstrated consistent precision 8-car stops, recall that when we did run in auto previously all stops were center platform and 8-car trains were run in manual.. the 2/3/5/6k with Alstom-based carborne ATC is fatally flawed in that it doesn't use an accelerometer to guide station stopping profiles and therefore has never worked correctly.. it is my understanding that Ansaldo, supplier of 7K ATC equipment, has yet to deliver an accepted solution either, 7Ks in testing tend to stop short or overrun more often then hit the target.

The original equipped 1k cars counted wheel turns that was tripped when the train passed over the 4 set marker coils. The distance of a wheel turns could be calibrated based on re-truing of the wheel profiles and or wear. The 4 set marker coils provided the train the ability to dial itself in to make precision station stops.

[farecard]

I have always thought the design approach was flawed/stuck in 1975.

There now exist low cost laser/microwave rangefinders. Put a reflector target X feet past the end of the platform.
The cab car end has the emitter/detector. As the train approaches it locks up and knows (to a few centimeters) the distance,
and stops accordingly. If it fails to detect by Y, it alerts and stops short.

[Sand Box John]

farecard
I have always thought the design approach was flawed/stuck in 1975.

There now exist low cost laser/microwave rangefinders. Put a reflector target X feet past the end of the platform.
The cab car end has the emitter/detector. As the train approaches it locks up and knows (to a few centimeters) the distance,
and stops accordingly. If it fails to detect by Y, it alerts and stops short.

The only thing flawed about it, is how it was not diligently maintained during the long period of time when WMATA did not routinely dispatch 8 car trains. As I pointed out above the rolling stock would calculate π to execute precision station stops. However if the circumference hard coded in to the rolling stock did not match the actual circumference of the wheel, station stops became imprecise.

380 prism reflectors would need to be kept clean for laser based measuring, they are not as cheap as you may think. With all of the various objects in WMATA's tunnels, a radar based system would need to be capable of distinguishing the target from the surrounding noise.