[PRCo] Re: MetroRail Signalling

[Schneider Fred]

Russ Jackson called me this evening ... I finally had an opportunity  
to ask him to explain the Washington Metro signal / ATO / ATC system.

His answer is simple.   It is fundamentally no different from the old  
Pennsylvania Railroad signals that I understood except that it uses a  
signal frequency in the audible range ... if amplified you would be  
able to hear it ... the frequency is in the 1000s of cycles per  
second instead of in the 100s of cycles per second.   According to  
Russ, the result is that the use of this higher frequency means that  
you do not need insulated joints because the signal current dies out  
in a short distance ... the block length is determined by how far  
down the rail the current will go before dying out.    The only place  
you need insulated joints is where you have very short blocks such as  
interlocks.   You do not need them for train detection over longer  
distances.

In general, otherwise the system would be the same as anything you  
understood in 1940 or 1950 or 1960.  The signal relays are fail  
safe.   They have to be energized to close.   The would be mounted in  
such a way that they open with gravity.   No current, they open and  
the trains get a command to stop.   No current in the circuit gives a  
train a stop command.

A current has to be used to give a speed command.   There had to be  
power in the circuit to give the train a command to crash into the  
train ahead of it.

Then Russ went on to bring in a major accident a Clapham Junction in  
London ten years ago.   In that case he explained that they later  
discovered that someone had installed a new relay.   A loose wire had  
later fallen across another wire and energized a signal circuit that  
should not have been energized.

Shit happens doesn't it.

Does this give the explanation you need?   It does clarify it for  
me.   It allows me to understand that you can have continuously  
welded rail and you do not need insulated joints.   At the point  
where the signal current dies out, you simply create a new current.

Now what happens if you are running in ATO.   The signal system  
imposes speed commands for the following trains.

And if you are running in manual?   You run at any speed up to but  
not over the speed commands that you would have in ATO because those  
commands are still there.   If you are in ATO and the track circuit  
allows 70 mph, you will not be allowed more than 70 in manual or the  
train will automatically brake anyway.   If you are one block two  
blocks behind a stopped train and for want of another number, the  
track speed allows 45 mph, you will not be allowed more than 45 if  
you are running in manual or ATO.


On Jun 29, 2009, at 4:46 PM, Herb Brannon wrote:

> To help fill in a small amount, I can offer the following tiny bit of
> information.  I will, however, go to the GCRTA Rail Training  
> Department and
> check on manuals which explain the cab signal system. RTA uses the  
> same
> system as Washington. Most of the systems are identical, with only  
> local
> variations. We were only give an overview of the operation of the  
> system
> when I was training for rail operator, but I will check for more in  
> depth
> manuals.
> The circular wires you mentioned are the "Wee-Z Bonds" mentioned in  
> one of
> the other posts. The box in the center of the rails is, more or  
> less, a
> transmitter/receiver which conveys information to and from a train  
> passing
> over the box. Until I read that post I had thought "Wee-Z Bond" was  
> a name
> applied locally in Cleveland to that device. I guess that's its  
> real name. I
> know RTA has continuous welded rail. There are no gaps in the rail.
>
> I had to forget everything I was taught in training at PATransit,  
> that was
> 'then' and 'now' is light-years ahead of 'then'. Even the newest  
> signal
> system at PATransit when I was there was on the South Patway in the  
> joint
> bus/street operations from Saw Mill Run bridge south to Ansonia  
> Street. That
> system was nothing compared to today.
>
> RTA does not gap the power supply at the Wee-Z Bond locations. Even  
> though
> we use overhead cantenary as opposed to third rail, it is the same
> thing......just elevated above the trains. [This was done at the  
> request of
> the private railroad companies running along side, over and under  
> the rapid
> tracks as a safety measure to protect the railroad workers circa  
> 1954.]
> There are circuit breakers at many locations, but not in direct  
> relationship
> to the Wee-Z Bonds.
>
> Like I said, I will get what I can (and they are always very  
> helpful and
> good about giving out manuals} from the RTA Rail Training  
> Department. I need
> to upgrade my memory banks on this subject also.
>
>
>
>
> On Sun, Jun 28, 2009 at 2:58 PM, Phillip Clark Campbell  
> <pcc_sr at yahoo.com>wrote:
>
>> Mr.Alan Schneider;
>>
>> Thank you very much for this report.  Thank you to the many  
>> contributors on
>> this subject.  The news reports  'seem'  well done and I was able  
>> to glean
>> much information from them;  comments from contributors  
>> underscored these
>> observations and brought much clarity to this disaster.  The  
>> postings have
>> been
>> most productive  --  'mostly.'
>>
>> I have changed the subject line and have questions to seek a greater
>> understanding
>> of the signaling system.  I found the URL for the included article:
>> http://www.fredericknewspost.com/sections/news/display.htm? 
>> StoryID=91910
>> because I wanted a closer look at the included photo:
>> http://www.fredericknewspost.com/photos/09/06/26/91910_large.jpg
>>
>> It is already established that  'computers'  handle the signals  
>> through
>>  'ATC;'  while I
>> understand the concept I am not familiar with the details.  My  
>> reference is
>> the US&S
>> signals as used on PRC interurbans.  Rails were gapped and  
>> insulated;  an
>> impedance
>> bond allowed ground return around the insulated rails while  
>> keeping the
>> signal circuit
>> current within the block.
>>
>> 'Parallel'  construction is evident in the MetroRail photo but the  
>> rails
>> are not gapped and
>> insulated are they.  Please note the dual set of cables between  
>> the rails
>> in each track
>> that arc through a half circle before attachment to each of the  
>> rails;
>>  this  'suggests'  an
>> insulated gap in the rails which, again, is not clearly evident.   
>> There are
>> far more cables
>> between the rails than the parallel US&S impedance bond.
>>
>> Also noteworthy is the large gap in the 600-volt(?) 3rd-rail.  As the
>> cabling between the rails
>> of each track seems identical and the 3rd-rail is gapped on both  
>> tracks I
>> am  'assuming'  that
>> such a gap in the 3rd-rail exists wherever such  'signal cables'   
>> exist.
>> Is this true?  Why is
>> it necessary to gap the power supply at signal cabling locations?   
>> Why
>> aren't the running
>> rails gapped, or are they?  I assume each truck has a 3rd-rail  
>> shoe on each
>> side;  it then
>> 'seems'  that current is never disconnected from the train as the gap
>>  'seems'  shorter than
>> truck spacing, or is it?  The right hand track has ties that  
>> extend further
>> than standard
>> 'apparently'  to accommodate 3rd-rail in the gap area;  the same  
>> may be
>> true of the other
>> track but the ties could be covered by the ballast.
>>
>> If someone is able to give some clarity to the computer style ATC  
>> signals
>> circuits it will
>> be most appreciated.  Thank you to one and all for such efforts.
>>
>>
>>
>>  Phil
>> Without  a   'coast'   but  not  a   'cause.'
>> --  --
>> "If thou wouldst rule well, thou must rule for God,
>> and to do that, thou must be ruled by Him ...
>> Those who will not be governed by God...
>> ........will be ruled by Tyrants."
>> William  Penn,  founder  of  Pennsylvania
>>
>>
>>
>>
>>
>> ________________________________
>> From: "alschneider2 at juno.com" <alschneider2 at juno.com>
>> To: etennyson at cox.net
>> Cc: rejmhj at netzero.net; j_swindler at hotmail.com; pcc_sr at yahoo.com;
>> pittsburgh-railways at dementia.org; jack.may at americomm.net;
>> gary-elaine at comcast.net; nawdry at bga.com; crvlkotula at aol.com;
>> philgcraig204 at yahoo.com; billvigrass at verizon.net;
>> bob.dietrich1 at verizon.net; bbente at bellsouth.net; trams2 at comcast.net;
>> allmanr at verizon.net; shadow at dementia.org; akftrain at aol.com;
>> miklosfrank at comcast.net; jaurelius at centurytel.net;
>> russell.jackson at stvinc.com
>> Sent: Sunday, June 28, 2009 10:27:36 AM
>> Subject: Re: METRORAIL DISASTER-DEFFERED MAINENANCE?
>>
>>
>> FrederickNewsPost.com
>>
>> Source: Metro circuits were malfunctioning for five days
>> Originally published June 26, 2009
>>
>>
>> By Marge Neal
>>
>>
>>
>>
>>  Photo by Associated Press
>>
>>
>> Workers install new fencing Wednesday in Washington, at the site  
>> where two
>> Metro trains crashed Monday.
>>
>>
>>
>>  Two track circuits in the area of Monday's deadly Metro crash  
>> alternately
>> reported the track as vacant and then occupied almost constantly  
>> from June
>> 17, when a part of a signaling device was replaced, until the time  
>> of the
>> crash, according to a Metro source.
>> The circuits appeared to have intermittently lost track of the trains
>> involved in the crash of two Metro trains that killed nine people,  
>> according
>> to Metro documents obtained by The Frederick News-Post.
>> The documents show what is known as "flip-flopping," with the circuit
>> alternately reporting the track as "occupied" and then "vacant."  
>> The report
>> for track circuit number B2-304, where the stopped train was  
>> located, starts
>> at 4:45 p.m. and ends at 5:38 p.m., about 40 minutes after the crash.
>> Throughout the time period covered by the report, the circuit  
>> shows the
>> track either occupied or vacant as often as every couple of seconds.
>> At 4:57:03 p.m., about the time of the crash, the report shows the  
>> track to
>> be vacant until 5:37:44, when it reports the track is occupied.  
>> Less than a
>> minute later, the report again states the track was vacant, even  
>> though
>> train wreckage was on the track. One second after that, the track was
>> reportedly occupied again. The circuit flip-flopped again before  
>> finally
>> showing the track to be occupied at 5:38:40.
>> On June 17, a part of the track signaling device known as a Wee-Z  
>> Bond was
>> replaced in the area of the crash, according to a Metro source who  
>> spoke on
>> the condition of anonymity. The Frederick News-Post agreed to the  
>> request
>> because of the compelling nature of the information.
>> The two track circuits involved in the crash -- B2-304 and B2-312  
>> -- share
>> the bond that was replaced. The component feeds the receiver for  
>> one and
>> gets the signal from the transmitter for the other.
>> Both circuits continued to alternately report the track as vacant  
>> and then
>> occupied almost constantly from June 17, when the part was  
>> replaced, to the
>> time of the crash, according to the Metro source.
>> "Without seeing the schematic drawings of the (Wee-Z Bond), I  
>> cannot say it
>> failed or contributed to this crash," Najm Meshkati, professor of  
>> civil and
>> environmental engineering at the University of Southern  
>> California, said
>> Thursday. "I can say the system did not get back to its normal  
>> operating
>> mode after the replacement was made."
>> The replacement part did not perform its intended purpose,  
>> Meshkati said.
>> The part could have been defective, or it could have needed to be
>> recalibrated or reset to work properly, he said.
>> Metro, he said, needs to take a "hard look" at its systems safety  
>> practices
>> and philosophy.
>> "It is important not to blame," he said. "It's important to find  
>> the root
>> cause of the problem and change the safety culture of the  
>> organization."
>> The Frederick News-Post has also learned that Matthew L. Matyuf,
>> superintendent of the Automatic Train Control division, was  
>> relieved of his
>> duties after the crash.
>> "I can confirm that the ATC superintendent has been temporarily  
>> assigned to
>> a special project," Lisa Farbstein, Metro's chief spokeswoman, said
>> Thursday. "It happened post-incident, and I do not know what the  
>> project
>> is."
>> Wednesday night, investigators from the National Transportation  
>> Safety
>> Board conducted tests using a similar train at the crash site,  
>> according to
>> a press release from the agency. When the train was stopped at the  
>> same
>> location as the stopped train that was hit, the train control  
>> system lost
>> detection of the test train.
>> Investigators are continuing to examine trackside circuits and train
>> control system data to understand how the train control system  
>> functioned on
>> the day of the crash, according to the release.
>> Recorder data have been recovered by the struck train. The  
>> striking train
>> did not have any onboard accident data recorders, according to NTSB.
>> The operator of the striking train, Jeanice McMillan, was killed  
>> in the
>> impact. NTSB investigators found metal-to-metal compression streak  
>> marks on
>> both rails of the track for about 125 feet ending near the point  
>> of impact,
>> consistent with heavy braking, the release states.
>> McMillan apparently pressed a "mushroom" button to activate an  
>> emergency
>> brake.
>> The operator of the struck train was interviewed Thursday morning,
>> according to the release. He told investigators that he operated  
>> his train
>> in manual mode during his entire shift that afternoon. He said he had
>> stopped to wait for a train that was stopped in front of him when  
>> his train
>> was struck.
>> NTSB said investigators will continue to document evidence at the  
>> accident
>> scene and intend to conduct sight distance tests using trains  
>> similar to
>> those involved in the crash.
>>
>>
>>
>>
>>
>>
>
>
> -- 
> Herb Brannon
> On America's North Coast  <TM>
> That's another fine mess you've gotten me into.
> *Oliver Hardy** *
>
>
>