Re: WMATA crash & track circuits

Dave Platt wrote:
In article <7i29pgF3000j1U1@xxxxxxxxxxxxxxxxxx>,
Joerg <news@xxxxxxxxxxxxxxxxxxxxx> wrote:

Why on earth did they never consider a system that has worked reliably for many decades in Europe, Indusi?

No relays, contacts or stuff that can corrode. There aren't too many explanations in English about it but this link contains one on page 3:

http://www.ovar.ca/Interchange/nov2001.pdf

It says "new" while in fact my late grandpa (a steam locomotive engineer in Germany) explained this system to me when I was a kid. If a train engineer screws up the emergency brakes are automatically applied and the train comes to a dead stop. It would have saved many lives in the US.

The Indusi system as described in the article you cite appears to be a
unidirectional "signal -> train" communication system. It looks to me
as if it depends on each individual signal source (e.g. road crossing,
train detector) working reliably, by itself... if it does, then it
ought to be pretty reliable in doing what it does.

It does not, by itself, seem to deal with the question of the
reliabiliy of the signal sources themselves - e.g. "train still on the
tracks" detection. It doesn't seem to be a detector... just a
communicator.

That latter aspect of the problem (the detector) is apparently what
failed in the WMATA crash. The "is there a train on this section of
the track?" detection process failed, due to the parasitic oscillation
and the undesired signal path within the detection system.

For this reason, it looks to me as if adding the Indusi system would
not have prevented this crash. It would have ensured reliable
communication from the "Is there a train on the track ahead?" sensor
to the train... but since the sensor system was malfunctioning and
"believed" that the track was clear, there would have been no STOP or
EXPECT STOP signal through the Indusi pathway, and the rearmost train
would still have been traveling at full speed.


I only know descriptions in German which won't help here. One component of the German system is the inductive axle counter. If 28 axles have entered a track section and any number smaller than 28 has left it then this section will remain blocked by Indusi. They don't like to rely on anything with electrical contacts over there, and I certainly wouldn't either.


It wasn't that an "engineer screwed up" - it's that the detector
screwed up, and gave the engineer wrong (but apparently authoritative)
information.


Not on this one. That was in L.A., IIRC he was text-messaging and then crashed. A properly installed Indusi system would have saved 25 lives. Most likely also in DC because the "section occupied" information would have been inductively picked up and registered.

I guess now they'll investigate whether the transistor stage oscillation was a one-time fluke or a design error, and (hopefully) why the track relay circuit was susceptible to a high frequency signal that it shouldn't be listening to. Hopefully the parties involved have good insurance.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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