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DC Metro Collision

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Posted by Jerry Pier on Wednesday, June 24, 2009 6:22 PM

My saying LTK designed the cars is misleading. They wrote the specm as did PBQ&D, for Bart but Rohr was responsinble for designing a car that met thoise specs in each case.

With respect to the Marta cars, I was involved in that contract only briefly but it could well have been. have been LTK.

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Posted by harpwolf on Wednesday, June 24, 2009 11:10 PM

We in San Francisco are watching this with keen interest, as our BART system also uses ATO (automatic train operation. 

 

Media is saying the lead car in the second train was a "B" car.  That doesn't sound right to me at all, I thought B-cars did not have a cab or controls adequate for more than shunting. Anyone know more?

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Posted by ValleyX on Thursday, June 25, 2009 9:30 AM

 

20 seconds to stop in a quarter mile? Which figures out to running 45 MPH and coming around a curve and reaction time, believing you're seeing what you shouldn't be seeing and taking action accordingly.  I've no idea but some of you might know what the stopping distances are on light rail trains such as this, a quarter mile isn't much 

Oh, and as for Casey Jones, yes, he did have quite a record but he was a product of his times, too. 

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Posted by Phoebe Vet on Thursday, June 25, 2009 9:46 AM

At 45 mph it would take 20 seconds to travel a quarter of a mile with no braking.

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 10:26 AM

At a deceleration or braking rate of -1.0 MPH per second [-1.5 ft./ sec. per sec.] - which is a very slow figure, almost unbelievably so - I figure the time to stop at 45 seconds and the distance at about 1,520 ft. after the brakes are applied [D = 1/2 x Decel. Rate in ft./sec. per sec. x Time squared, in secs.], plus the distance traveled during the operator's perception and reaction time.  If we allow 2 seconds for that at 45 MPH = 66 ft. / sec. for 132 ft., then the total time is 47 seconds and the total distance is about 1,650 ft. = 0.31 mile.

At a decel rate of 2.0 MPH per second - still pretty slow - the braking time is 22.5 secs., and the distance is about 760 ft., for a total time of 24.5 secs. and a total distance of about 890 ft. = 0.17 mile.

At a decel rate of 3.0 MPH per second - more realistic - the braking time is 15.0 secs. and the distance is about 505 ft., for a total time of 17 secs. and a total distance of about 640 ft. = 0.12 mile.

Even if only a quarter-mile's distance and visibility was available to stop, if the operator reacted promptly by then the train should have stopped, or been moving much slower than it apparently was.

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Posted by DMUinCT on Thursday, June 25, 2009 10:26 AM

Phoebe Vet

selector

I'm going to stick my neck in here and state that what you pay a person and how they orient themselves to their work are very poorly related.  Recent history of the work and moral ethics of people at all social and financial strata will support me.  Was the texting engineer from last fall paid minimum wage?  Was Madoff paid minimum wage?  My wife works at a slightly above minimum wage job at a popular coffee chain up here in Canada, and I can asure you that she brings her all to her work because that is her nature.

We should stick to sensible premises.

-Crandell

Crandell:

I don't think the contempt that you read in that "minimum wage" comment was directed at the motorman so much as at the employer who feels that the operator monitoring the computer is worth less than the one who is actually manipulating the controls.

The wage paid for a given job does not have much of an effect on the employee's motivation.  It does, however, seriously impact the quality of people who apply for the job when it is vacant.  When the pay is low, you get few applicants and often must hire some people that you wouldn't otherwise.  You will get some good ones, but they will probably always be looking for something better.  When you pay well, you get many applicants and you can be very fussy about which one you hire.

Sometimes low wages are all that can be offered because there is not enough markup in the end product to support higher.

I have no idea of the pay scale of a Subway Motorperson.  In Washington DC it must be a Union Scale.

As for up here in Boston, Commuter Rail is B.L.E./United Transportation/Teamster Union.  Locomotive engineers who work a split shift (morning rush hour - afternoon rush hour) can make more than $100,000 a year.  With there F40PH or GP40MC, they drive 6 and 8 car trains at 80mph.

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Posted by Deggesty on Thursday, June 25, 2009 11:03 AM

Paul_D_North_Jr
Even if only a quarter-mile's distance and visibility was available to stop, if the operator reacted promptly by then the train should have stopped, or been moving much slower than it apparently was.

We cannot know how long it took the operator to react; could it not have taken longer than two seconds?

Johnny

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Posted by carnej1 on Thursday, June 25, 2009 11:06 AM

DMUinCT

Phoebe Vet

selector

I'm going to stick my neck in here and state that what you pay a person and how they orient themselves to their work are very poorly related.  Recent history of the work and moral ethics of people at all social and financial strata will support me.  Was the texting engineer from last fall paid minimum wage?  Was Madoff paid minimum wage?  My wife works at a slightly above minimum wage job at a popular coffee chain up here in Canada, and I can asure you that she brings her all to her work because that is her nature.

We should stick to sensible premises.

-Crandell

Crandell:

I don't think the contempt that you read in that "minimum wage" comment was directed at the motorman so much as at the employer who feels that the operator monitoring the computer is worth less than the one who is actually manipulating the controls.

The wage paid for a given job does not have much of an effect on the employee's motivation.  It does, however, seriously impact the quality of people who apply for the job when it is vacant.  When the pay is low, you get few applicants and often must hire some people that you wouldn't otherwise.  You will get some good ones, but they will probably always be looking for something better.  When you pay well, you get many applicants and you can be very fussy about which one you hire.

Sometimes low wages are all that can be offered because there is not enough markup in the end product to support higher.

I have no idea of the pay scale of a Subway Motorperson.  In Washington DC it must be a Union Scale.

As for up here in Boston, Commuter Rail is B.L.E./United Transportation/Teamster Union.  Locomotive engineers who work a split shift (morning rush hour - afternoon rush hour) can make more than $100,000 a year.  With there F40PH or GP40MC, they drive 6 and 8 car trains at 80mph.

 I was under that impression that all the MBTA light rail operators were under a different union than the commuter rail people?

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 12:29 PM

Deggesty

Paul_D_North_Jr
Even if only a quarter-mile's distance and visibility was available to stop, if the operator reacted promptly by then the train should have stopped, or been moving much slower than it apparently was.

We cannot know how long it took the operator to react; could it not have taken longer than two seconds?

Johnny

It very well could have taken her longer than 2 seconds, but to my mind only if she either - 1. wasn't paying attention, or 2.  'froze' at the controls.  Either one is problematic to me. 

My understanding is that something between 1.5 and 2 seconds is the usual standard/ time allowance for a person to see something, comprehend it, and to react in a simple way, such as stepping on the brake in a car - or appying the emergency brake of a train - or to start to react in a more complex way.

- PDN.   

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 12:41 PM

Today's [June 25, 2009] Wall Street Journal - on page A-3 - has an article headlined 'D.C. Train Probe Finds Flaw in Control System', by Christopher Conkey in Washington, D.C.  The short version is that anomalies - of an unspecified nature - were found in a 740-ft. long circuit, 1 of 6 circuits between the Takoma and Fort Totten stations.  The full story is at;

http://online.wsj.com/article/SB124584588523747057.html 

- PDN.

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Posted by BaltACD on Thursday, June 25, 2009 12:45 PM

Local news had a sound bite from the NTSB spokesperson that there was approximately 400 feet of top of rail 'blueing' prior to the collision site...indicative of wheels sliding on the top of rail with an emergency brake application.  How long it would take the brakes to apply to maximum pressure to lock the wheels is another question.  Maximum speed in the area is reported to be 59 MPH.  NTSB is currently reported to be investigating a malfunctioning 'track circuit' and it's interaction in the Metro operations computer system.

 

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Posted by BigJim on Thursday, June 25, 2009 12:49 PM

Paul_D_North_Jr
Even if only a quarter-mile's distance and visibility was available to stop,


How many of us know what kind of sight distance the operator had? From one of the pictures printed in the paper, it didn't look like much to me. The train was in a right hand curve and at least partially hidden by a fence between it and the track to the right.

I will relate one incident to you. While running on a clear signal, travelling down grade at 40mph on wet rail with one four axle unit and three old CR heavyweight geometry cars, I came around a curve to see a Stop signal maybe 3/8ths of a mile ahead. My first thought was to make a normal stop which would have taken us past the stop signal. My next thought was, naw, I don't want to go through the hassle of the dispatchers taking forever to run a log on the signal, even though I knew we couldn't be disciplined for passing the red board. My next action was to put the train in emergency. Guess what? We stopped about five car lengths BEFORE passing the signal. Now, go figure all of that up.

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 1:30 PM

Seems pretty consistent to me.  4-axle unit - which model [Q]  Anyway, a lot of weight on only 4 axles, so good adhesion even with the wet rail.  Short train, so quick response by all brakes.  How steep was the down grade [Q]  Presuming you used sand, too [Q]

The math -

3/8 mile [5,280 ft.] = 1,980 ft., say 2,000 ft. distance from the signal when observed = 0.38 mile.

5 [freight] car lengths at 60 ft. = 300 ft. from signal when stopped.

Distance used to stop = 1,700 ft. [2,000 ft. - 300 ft.] = 0.32 mile.

40 MPH = 60 ft./ sec., so 2 seconds reaction time = 120 ft. traveled before brakes applied.

Net distance traveled to stop while brakes applied = 1,700 - 120 = 1,580 ft. = 0.30 mile.

Solving the D = 1/2 x A  x T squared equation for T, I get about 53 seconds to stop, at an average deceleration rate of about -1.15 ft. / sec. = -0.78 MPH per second. 

That's well within the bounds of reason for a short mainline passenger train in emergency, even considering the effect of the downgrade.  Does it seem about right to you for that situation [Q]

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Posted by HarveyK400 on Thursday, June 25, 2009 3:38 PM

ValleyX

 20 seconds to stop in a quarter mile? Which figures out to running 45 MPH and coming around a curve and reaction time, believing you're seeing what you shouldn't be seeing and taking action accordingly.  I've no idea but some of you might know what the stopping distances are on light rail trains such as this, a quarter mile isn't much 

Oh, and as for Casey Jones, yes, he did have quite a record but he was a product of his times, too. 

 

One thing I noticed was high chain link fences separating WMATA and CSX tracks, substantially reducing visibility around the curve at a more acute angle.  I certainly can't say to what degree this may be a factor.

I think the trains can brake at 3mphps at full service.  It can probably stop from 55 mph in about an 1/8 of a mile in good conditions; but I don't have any definitive information and haven't worked it out. 

 

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Posted by sigma693 on Thursday, June 25, 2009 3:44 PM

 Just read a headline...  'METRO to inspect every stretch of rail on system' .   Great, NOW they spend the time and money to INSPECT THEIR system! 

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 4:28 PM

HarveyK400
  [snip]  I think the trains can brake at 3mphps at full service.  It can probably stop from 55 mph in about an 1/8 of a mile in good conditions; but I don't have any definitive information and haven't worked it out. 

Earlier today I saw a Wikipedia article on the WMATA cars [usual disclaimers apply], and it had data for the max. braking rate for the newer cars - those were all in the 3.0 MPH per sec. and slightly better range.

Working through the math, the braking distance would be about 760 ft. = 0.14 mile, just over the 1/8 mile = 0.125 mile stated, or maybe a little less, so that seems about right.  If we again allow 2 seconds for operator reaction time, at 55 MPH = 81 ft. / sec., that adds 162 ft. for a total of about 920 ft. or 0.17 mile = 3/16th mile.

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Posted by beaulieu on Thursday, June 25, 2009 5:59 PM
Interesting findings today. When the NTSB recreated the accident today and stopped another train at the exact location of the accident Metro's Control Center lost detection of the train on track circuits.
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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 7:21 PM

Yes, very interesting - to say the least. 

Pick one - or more, as appropriate:  Black Eye  Shock  Sad  Disapprove   Confused  Whistling  Grumpy

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Posted by blue streak 1 on Thursday, June 25, 2009 7:33 PM

Paul_D_North_Jr

Yes, very interesting - to say the least. 

Pick one - or more, as appropriate:  Black Eye  Shock  Sad  Disapprove   Confused  Whistling  Grumpy

     PDN::   Whistling    Goes back to my earlier  post!!!!!!!!

 1.  Computer control  --  OH Boy!!  First the obvious. Track detection circuit failed to note train that was run into.

 

2. Computer control  -- Why did computer not have software that will shut down area if a train gets lost?

3. Does the system operate in parallel with another computer and if not why? and if so why not shut down when there is a discrepancy?

4. Was a software patch installed sometime before this crash?

5. Three trains in a block? Did this fool the computer?

7. Is this putting too much reliance on one system without an independent backup?

9.  GIGO? (garbage in garbage out)

10. How many more possible computer problems can we come up with?

Now lastly could the computer have not allowed the emergency braking to start immediately but had a delay built in?   Not likely but------------------  

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Posted by Paul_D_North_Jr on Thursday, June 25, 2009 7:43 PM

 Yep, sadly enough.  Machines and systems are not infallible - still subject to the errors and omissions of human design, construction, installation, and maintenance.

Oh - were 6. and 8. edited out, or deleted ?  Confused 

 - PDN.

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Posted by henry6 on Thursday, June 25, 2009 7:43 PM

"Now lastly could the computer have not allowed the emergency braking to start immediately but had a delay built in?   Not likely but------------------ "

 

Then could the computer apply the brakes and at the same time apply power to the motors?

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Posted by BigJim on Thursday, June 25, 2009 10:10 PM

"Seems pretty consistent to me.  4-axle unit - which model [Q]" 
GP38

"How steep was the down grade [Q]"
1.5% 

"Presuming you used sand, too [Q]"
Automatic with Emerg. application

"Does it seem about right to you for that situation [Q]"
What it did was make a true believer out me about a story one of my mentors once told me. I'll save that one for another day. 

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Posted by HarveyK400 on Friday, June 26, 2009 12:07 AM

To lose a train, sufficient signal strength must reach the preceding block or following train to energize the track relay despite partial shunting of the rails.  (Broken rails, etc, also interrupt the track circuit.)  Even if a train was lost by the train control system, a restricting approach signal protecting the train at the station was generated, bringing the struck train to a halt and should have slowed the following train.

While certainly bad, the failure to detect the struck train does not explain a speed in excess of an approach at which the following train was traveling in ato mode and would have been brought to a stop in about the same location as the struck train. 

The only plausible explanation is that, in the absence of a strong signal, a leaking cross-talk "clear" signal from the adjacent track was picked up by the following train, allowing it to proceed at greater than a reduced speed approaching the block occupied by the train at the station. 

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Posted by Bartle1 on Friday, June 26, 2009 4:40 AM

From over in the UK this accident has some similarity to the Clapham accident here about 20 years ago. Happened on a Monday after weekend work. Train 1 stops and is unusually delayed. Train 2 stopped correctly at signal behind it. Train 3 signalled straight through by signalling system. All down to incorrect wiring job in the interlocking, this was the first such combination of stopped trains after the rewiring work.

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Posted by oltmannd on Friday, June 26, 2009 7:59 AM

HarveyK400

To lose a train, sufficient signal strength must reach the preceding block or following train to energize the track relay despite partial shunting of the rails.  (Broken rails, etc, also interrupt the track circuit.)  Even if a train was lost by the train control system, a restricting approach signal protecting the train at the station was generated, bringing the struck train to a halt and should have slowed the following train.

While certainly bad, the failure to detect the struck train does not explain a speed in excess of an approach at which the following train was traveling in ato mode and would have been brought to a stop in about the same location as the struck train. 

The only plausible explanation is that, in the absence of a strong signal, a leaking cross-talk "clear" signal from the adjacent track was picked up by the following train, allowing it to proceed at greater than a reduced speed approaching the block occupied by the train at the station. 

I don't think you have it right.  You are right about the trailing train having to see a "clear" on board, but a failure to shunt the track circuit is exactly what could have caused this mess. If the block of the train ahead was sending "clear" to that train and the train didn't shunt the track circuit, the signal behind the train would also see the "clear" coded track circuit signal coming down the rails and would send "clear" out down it's block to the following train.

 A broken rail in a block would have stopped the following train. Since the "clear" being sent down to the trailing signal would never make it past the break.  It would look just like an occupied block to the trailing signal.  No code being received.

In response to some other posts...

The "Control Center" with the computer is not the safety system.  The block signal system is.  It doesn't matter if the dispatching system lost the train in it's train tracking system or not.  It's only a supervisory control system, not a safety system. What keeps the trains apart is a good old fashioned fixed block signal system where all the "vital" hardware is located on the wayside.  (with inductive cab signalling and penalty braking/speed control system to active brakes when the train is not operating in accordance with the signal indication.)

The Control Center gets information from the field in order to be able to manage operations, but there is no guarantee that the information it gets and process is correct.  It can use this information to make decisions about which switches to throw and what routes to clear, but whether or not the switch actually throws and what aspect the signal system displays in fully in the hands of the wayside equipment.

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Posted by DMUinCT on Friday, June 26, 2009 8:50 AM

There you go agin, talking trains.

This is a Subway System that came out of the tunnel and was running on the surface.  A 4 track line with the center 2 tracks used for Subway, third rail power, fenced on both sides to keep the kids (and others) off the third rail.

The cars are light weight with traction motors on each car. A Computer sends signals to the train (not the operator) telling it when to run, when to stop, and how fast it should be running.  To be any good the train must acknowledge the command back to the computer.  If the Train loses contact with the computer it must default to stop!!!

Amtrak's Northeast Corridor does it right.  The engineer runs the locomotive, he is checked twice a minute by the Alerter.  If the engineer sees a Restrictive signal he also gets a Cab Signal which he must acknowledge.  If he over runs the signal the ATC takes over and slows the train to the proper speed. (he must still acknowledge the Alerter or the brakes go on)

This system requires a fully trained and qualified Engineer in the cab.

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Posted by zardoz on Friday, June 26, 2009 8:54 AM

(bold highlights mine) 

WASHINGTON (AP) -- A memorial service will be held for the operator of a Washington Metro train involved in Monday's crash.

Jeanice McMillan, 42, of Springfield, Va., was to be remembered Friday morning at the Temple of Praise Fellowship Hall in D.C. Her brother and members of her local union are expected to speak.

McMillan and eight passengers were killed in the crash when her train barreled down the tracks and hit a stopped train. About 70 people were also injured.

The train was on automated control at the time of the crash and investigators say they there is evidence McMillan applied the emergency brake before the accident.

Investigators said Thursday the computerized signaling system failed to detect a test train stopped in the same place as one that was struck during the crash.

http://hosted.ap.org/dynamic/stories/U/US_DC_METRO_TRAIN_DERAILMENT?SITE=WIKEN&SECTION=HOME&TEMPLATE=ap_content_popup.html

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Posted by Anonymous on Friday, June 26, 2009 9:49 AM

In regard to the amazing fact that the investigation test showed that the computerized signaling system failed to detect a test train stopped in the same place as one that was struck during the crash: 

This seems like a profound “smoking gun” that is highly likely to pinpoint the exact cause without any doubt.  Usually when they test equipment and signals after a collision, everything is found to be working properly.  However, with this repeat of the basic fault during the test, it seems like all they have to do now is find the mouse stuck in the relay or whatever.   

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Posted by HarveyK400 on Friday, June 26, 2009 9:55 AM

oltmannd
...You are right about the trailing train having to see a "clear" on board, but a failure to shunt the track circuit is exactly what could have caused this mess. If the block of the train ahead was sending "clear" to that train and the train didn't shunt the track circuit, the signal behind the train would also see the "clear" coded track circuit signal coming down the rails and would send "clear" out down it's block to the following train....

First, I agree that the wayside signal equipment protects train operation, not the central computer; and my remarks are predicated on that.  The computer having lost the train is incidental and only indicative of the problem.

I think you lost track of the fact that wayside equipment had brought the struck train to a halt; and as a result of not adequately shunting the block circuit, the following train would have recieved the same approach signal for a reduced speed, not a separate clear signal.

Someone made a comment that the signal blocks in that area were ~1,700' long - perhaps at the edge of the envelope.  Signal strength necessarily would be tuned higher to overcome the greater resistance inherent in the longer circuit which may have overcome the shunting.  In addition, traveling at reduced speed in compliance with cab signals, the train probably came to a stop at the end of the occupied or restricted block and partly in the preceding, approach, block reducing the shunting.

In the event a double red system is used, the struck train proceeding at track speed would receive a stop/restrictive signal upon entering the restricted block and brake to a stop in 900'-1,300' before reaching the block occupied by the train in the station.  Failing to fully shunt the circuit, the following 450' train would still have 450'-900' for braking with the restrictive indication before striking its leader.

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Posted by BaltACD on Friday, June 26, 2009 10:07 AM

HarveyK400

oltmannd
...You are right about the trailing train having to see a "clear" on board, but a failure to shunt the track circuit is exactly what could have caused this mess. If the block of the train ahead was sending "clear" to that train and the train didn't shunt the track circuit, the signal behind the train would also see the "clear" coded track circuit signal coming down the rails and would send "clear" out down it's block to the following train....

First, I agree that the wayside signal equipment protects train operation, not the central computer; and my remarks are predicated on that.  The computer having lost the train is incidental and only indicative of the problem.

I think you lost track of the fact that wayside equipment had brought the struck train to a halt; and as a result of not adequately shunting the block circuit, the following train would have recieved the same approach signal for a reduced speed, not a separate clear signal.

Someone made a comment that the signal blocks in that area were ~1,700' long - perhaps at the edge of the envelope.  Signal strength necessarily would be tuned higher to overcome the greater resistance inherent in the longer circuit which may have overcome the shunting.  In addition, traveling at reduced speed in compliance with cab signals, the train probably came to a stop at the end of the occupied or restricted block and partly in the preceding, approach, block reducing the shunting.

In the event a double red system is used, the struck train proceeding at track speed would receive a stop/restrictive signal upon entering the restricted block and brake to a stop in 900'-1,300' before reaching the block occupied by the train in the station.  Failing to fully shunt the circuit, the following 450' train would still have 450'-900' for braking with the restrictive indication before striking its leader.

Local reports are that the stopped train was not being operated in automatic control, but in manual control....Why the two trains were being operated in different manners then becomes a question.

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