Re: WMATA crash & track circuits

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.

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

--
Dave Platt <dplatt@xxxxxxxxxxxx> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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