It was on the national news. NBC had video of it at about 6:15 PM.
I just rode that line a few weeks ago.
Dave
Lackawanna Route of the Phoebe Snow
Just saw the latest video on local news. It looks as if one car pushed into another, with the upper shell of the one wrapped around a reasonably intact car below. Not visible, what happened to the interiors of both cars.
If those cars were anywhere near filled to capacity, there will probably be many more dead recovered (the official count is now four.) The newscaster said that they had a mass casualty event, with no estimate of what the total might be.
It's way too early to try to figure out what happened - or didn't happen when it was supposed to. All we can do is mourn the dead and pray that the injured will make full, rapid recoveries. Later we can try to make sense of whatever materiel or human failure was involved, and what has to be done to drastically reduce the possibility of a repeat.
Chuck
http://news.yahoo.com/s/ap/20090623/ap_on_re_us/us_dc_metro_train_derailment
I hope there's wasn't any texting!
Local Television out of DC just announced that the death toll from the Metro accident is now 6.
Information is indicating that it was a rear end collision, as opposed to head on as was previously being reported.
Never too old to have a happy childhood!
ValleyXDoes anything know anything about the operation of the Metro DC system. I read on another forum that these trains are computer controlled with an operator override. Is there any truth to that?
It's automatic control. In normal operation the motorman only opens and closes the doors, and makes station announcements.
RWM
Railway ManValleyXDoes anything know anything about the operation of the Metro DC system. I read on another forum that these trains are computer controlled with an operator override. Is there any truth to that? It's automatic control. In normal operation the motorman only opens and closes the doors, and makes station announcements.RWM
Just saw about this on local news so I checked in. What a disaster, lets hope the casualties don't go any further.
One southbound train collided with another just under the New Hampshire Avenue Bridge near the Ft. Totten station on the Red Line
Update as of 10 PM: There are 70 injuries; 50 people who have minor injuries, 14 people who have moderate injuries, and 6 people who have serious injuries. So far there are 6 people who are known dead, but the Fire Department's Emeregency Rescue Service is still searching both trains for others.
NTSB is on the scene, but they can't begin their investigation until the Fire Department finishes its search and rescue opereation. One of the things they will be looking for is an event recorder which gives information such as time of day, speed, and whether the trains were under automatic or manual control. The General manger of Metro was interviewed, and he said it was standard procedure to have the trains on automatic [computer controlled] operation during rush hours. The Metro trains that crashed carried 6 cars, one train was one of the earliest series - 1000 series - while the other train was of the 5000 series;
In a choice between operator (i.e. human) error and technology breaking down...I will go with the latter.
Sounds like the crash on the MBTA Green Line in Newton, MA in May 2008... One train stops at a signal, another rear ends it. The operator was texting. Train speeds on the ex-B&A line are at least 40.
That wreck was close to the same train speeds (the MBTA train was doing 37 or 38 MPH) and it was an older (either from the 1986 / 1988 or 1997 orders) light rail vehicle involved, not a heavy rail subway. The car had a black box, unlike the Metro car, and all but the motorman survived.
I can see why people are mad at the Metro... If a Type 7 LRV can survive better than a heavy rail subway at comparable speeds, and has a black box recorder, which the Metro car does not, there's something wrong there!
As reported in other Forum replies, the "State of the Art" DC Metro was conceived to run without an operator, complete computer control. Safe, interesting features, Subway Stations without columns for crime prevention, a hidden compartment next to the Motorman so Transit Police can watch down the car un-observed. An Operator or Motorman was added just to guard the doors. When the motoman stepped off, 20 years ago, the train left without him, a "Start Button" was added in the cab. I have ridden them, read about the advances, I do not know the extent of "Cab Signals", "Stop", or "Overide" buttons and switches that are in the cab nor the amount of training required on a computerized system.
Something went very wrong that wasn't backed up.
Don U. TCA 73-5735
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
CShaveRRForgive me, but I've never ridden or followed the DC Metro system, so I'm not sure about their equipment (long and low, is all I remember from seeing some a few years ago). But we are dealing with some mighty old cars here. News reports say that the train that rear-ended the other one had old cars that should have been phased out years ago. The fact that the shell split away from the frame in the way it did attests to the lack of crashworthiness of that particular design. I suspect (at the risk of becoming too political here) that the short-changing of mass transit by past administrations and Congresses is to blame for old equipment being kept around longer than it should have been, given modern safety requirements. Even if the Metro were to become appropriately "stimulated" today, it would take years before these cars could be phased out.
I suspect (at the risk of becoming too political here) that the short-changing of mass transit by past administrations and Congresses is to blame for old equipment being kept around longer than it should have been, given modern safety requirements. Even if the Metro were to become appropriately "stimulated" today, it would take years before these cars could be phased out.
Along the same lines (sort of):
The cause of this crash will be determined by a full investigation that might take weeks. It is likely to be several days before one or more probable causes emerge and are reported. We will be told over and over not to jump to any conclusions until the investigation is complete. Yet today officials are reporting that the equipment comprising the train that struck the other was old and overdue for replacement. And they add that the failure to replace it was a safety concern. Specifically, they have linked the insufficient crashworthiness of the obsolete equipment to the damage suffered in this crash. I have not heard reports of any other linkage of the inadequate safety of the obsolete equipment to the crash, but perhaps there have been some.
I have to ask why any official would volunteer this incredibly sensitive and incriminating information before the official investigation has even begun. I can only conclude that it is evidence of an on-going agenda to lobby the public for more funding by highlighting the premise that inadequate funding increases danger to the public. What better tool could there be? It basically tries to blame the crash on the taxpayers.
But, at the same time, this tactic seems incredibly ham-handed for failing to see the unintended consequence. That is, when you blame unsafe equipment on a lack of funding, you acknowledge that you are placing the public in danger by knowingly running unsafe equipment.
BucyrusI have to ask why any official would volunteer this incredibly sensitive and incriminating information before the official investigation has even begun. I can only conclude that it is evidence of an on-going agenda to lobby the public for more funding by highlighting the premise that inadequate funding increases danger to the public. What better tool could there be? It basically tries to blame the crash on the taxpayers. But, at the same time, this tactic seems incredibly ham-handed for failing to see the unintended consequence. That is, when you blame unsafe equipment on a lack of funding, you acknowledge that you are placing the public in danger by knowingly running unsafe equipment.
I thought it was the National Transportation Safety Board (NSTB) that was making the statements, not the DC Metro itself.
Lets back up, IF the trains had not CRASHED, the construction of the cars would be a non-starter.
The damage is a result, not a cause.
When you start to ask questions, how do you get two outbound trains at the same place, on a double track, third rail powered, computer controlled line at the same time?
Bucyrus,
The NTSB is a political organization. They have a long list of wants/needs/got to haves for each mode. When something happens that seems to relate to something on their list they trot it out as you have seen in this case. I suspect the reason is that the media will carry the item in the immediate aftermath.
The final reports get very little media play but do contain recommendations to the operator and the appropriate regulatory agencies. They usually respond in writing to the NTSB. If the operator or regulatory agency agrees and says "we will do that, or we have done that" NTSB is happy and closes the item as acceptible, if I remember the term correctly. If the operator or regulatory agency disagrees NTSB closes it as unacceptable and waits for the appropriate accident to trot it out again.
It is all a political game. To their credit NTSB is very good at aircraft accidents and reconstructions but they give no thought to the cost or benefits of their recommendations. I think they are specificially prohibited from doing so, but am not sure of the law on that point.
Mac
TrainManTy Sounds like the crash on the MBTA Green Line in Newton, MA in May 2008... One train stops at a signal, another rear ends it. The operator was texting. Train speeds on the ex-B&A line are at least 40. That wreck was close to the same train speeds (the MBTA train was doing 37 or 38 MPH) and it was an older (either from the 1986 / 1988 or 1997 orders) light rail vehicle involved, not a heavy rail subway. The car had a black box, unlike the Metro car, and all but the motorman survived. I can see why people are mad at the Metro... If a Type 7 LRV can survive better than a heavy rail subway at comparable speeds, and has a black box recorder, which the Metro car does not, there's something wrong there!
IINM, the LRVs are much newer than the DC equipment so that may explain the lack of event recorders..
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Bucyrus...But, at the same time, this tactic seems incredibly ham-handed for failing to see the unintended consequence. That is, when you blame unsafe equipment on a lack of funding, you acknowledge that you are placing the public in danger by knowingly running unsafe equipment.
Agreed, and this raises distinct and troubling questions on ethics.
We should all hope, and expect patiently, that the facts are clear, simple and incontrovertible when they are revealed.
-Crandell
BucyrusI have to ask why any official would volunteer this incredibly sensitive and incriminating information before the official investigation has even begun.
All too often initial "blame" gets placed on some peripheral issue (like the age of the cars) when the actual cause of the incident was something totally unrelated. Granted, if the cars had been more crashworthy, the number of killed and injured might have been lower, but the fact remains that if [whatever the cause turns out to be] hadn't happened, the age of the cars would have been a moot point.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
The NTSB does a fine job, I know a member of the rail group, its not the same people as in an airline crash. BUT, they can only recommend, it's up to the Congress or State Governments to pass or change a law to include the recommendations. This has been done in the "Chatsworth Crash" but Congress has given the Railroads to 2015 to make the changes. We all know Calf. has lots of money!
AP News posted on Yahoo: for what it's worth.
The train that was hit (new type) had a "Black Box", the train that did the hitting (old type) did not.
The Driver of the hitting train, a 44 year old woman who was killed in the crash, was hired two years ago as a Bus Driver and later promoted to Trains.
During "Rush Hour Service" trains are run by the computers, off peak they sometimes are run manually.
carnej1The Green Line and the DC Metro use very different signal and train control systems . IINM, the DC trains are much more automated with the Human operators as emergency backup so I do not think that we can assume the same circumstances (although I'm not suggesting human error can be ruled out). IINM, the LRVs are much newer than the DC equipment so that may explain the lack of event recorders..
The Green Line and the DC Metro use very different signal and train control systems . IINM, the DC trains are much more automated with the Human operators as emergency backup so I do not think that we can assume the same circumstances (although I'm not suggesting human error can be ruled out).
I had no idea the Metro trains were automated... I can see how different they are now!
When were the Metro cars built?
TrainManTyWhen were the Metro cars built?
The first batch were built in 1976 by Rohr Industries in Winder GA. I believe they were designed by Breda of Italy.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
oltmannd TrainManTyWhen were the Metro cars built? The first batch were built in 1976 by Rohr Industries in Winder GA. I believe they were designed by Breda of Italy.
Very interesting- I railfan around Winder quite often and did not realize that the current Trinity facility (fomer Thrall, former Rohr) made thiose cars. Thanks for the info. Jamie
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Some additional information; The east leg of Metro's Red Line runs along the CSX Brunswick Line from the Rhode Island Avenue station to the Silver Spring Station; after leaving Silver Spring the Red Line enters a tunnel mostly under Georgia Avenue (MD 97) through Wheaton to Glenmont at the intersection of Georgia Avenue and Randolph Road (MD 97 and MD 182).
MARC's Brunswick Line trains were cancelled today (June 23), however, Amtrak's eastbound Capitol Limited did run, and I expect the Westbound Capitol Limited will run today.
The accident raises many questions which the NTSB will have to sort out. According to today's Washington Post the train that was hit had stopped behind another train that was standing in the Ft. Totten station. Metro's tracks run in between the CSX Metro Subdivision tracks, and north of the Ft. Totten station the tracks curve around under the New Hampshire Avenue bridge so one question is, was the operator's sight-line blocked so she couldn't see the other train until it was too late?
Unfortunately Metro Rail's safety record isn't too good. There were two incidents in the last 5 years where track workers were killed because the train opeerators did not reduce the train sppeds as they passed the work zones. The brakes failed on a Red Line train at the Shady Grove station causing the train to derail, and killing the operator. There was another incident 5 yeas ago where the brakes failed on an empty Red Line train which rolled downhill, and collided with a standing Red Line train which was stopped at the Woodley Park-Zoo station. In another indcident on the Orange Line two years ago where the operators of two trains, having clear signalsand under automatic control, noticed their trains were still too close to one another so they applied the brakes. And finally 2 years ago a Yellow Line train derailed at the Mt Vernon Square station, and it collided with the tunnel wall injuring 20 people.
PNWRMNM Bucyrus, The NTSB is a political organization. They have a long list of wants/needs/got to haves for each mode. When something happens that seems to relate to something on their list they trot it out as you have seen in this case. I suspect the reason is that the media will carry the item in the immediate aftermath. The final reports get very little media play but do contain recommendations to the operator and the appropriate regulatory agencies. They usually respond in writing to the NTSB. If the operator or regulatory agency agrees and says "we will do that, or we have done that" NTSB is happy and closes the item as acceptible, if I remember the term correctly. If the operator or regulatory agency disagrees NTSB closes it as unacceptable and waits for the appropriate accident to trot it out again. It is all a political game. To their credit NTSB is very good at aircraft accidents and reconstructions but they give no thought to the cost or benefits of their recommendations. I think they are specificially prohibited from doing so, but am not sure of the law on that point. Mac
DC Metro has had a history of scrambling for money just to maintain there level of operations, let alone come up with money to fund 'improvements' that won't necessarily either increase service or decrease costs.
In some instances the NTSB final reports have been swayed by politics.
When you consider the volume of passengers, Metro has a pretty good safety record which is much better than driving on the roads in the Washington area (which probably takes years off of people's lives due to pure stress level). No transportation system is totally safe - obviously as this accident shows - but when you consider that a fatal car accident would only get more than a little blurb in the Metro section of the Post if it involved something like street racing, it is easy to forget just how dangerous driving is since fatal car crashes are generally pretty mundane.
At first, when I saw the photos, I thought that the collision happened in Silver Spring, MD since it looked like Silver Spring where CSX tracks are on each side of the Metro tracks - the Red Line runs on both ends parallel to CSX tracks and often are right next to them (from Union Station to just north of Silver Spring on the east (Wheaton End) and from just north of White Flint to the end of the line at Shady Grove. The Red Line often offers views of rail action especially when approaching Union Station.
The Metro tracks use wooden ties (at least when above ground).
What I find is interestign is that this happened after so much emphasis was placed on worries about terrorism - did placing so much emphasis on the unlikely possibility of a terrorist bombing attack cause Metro to neglect the much realer possibility of system failure?
When I lived in the area and commuted on Metro, I generally rode in the first and last car because it was the least crowded (often when boarding at stations I boarded on (Rosslyn, Ballston, and Pentagon City mainly) it was impossible to board one of the center cars and you had little choice but to get in one of the end cars even though it was less safe.
The system does have funding problems - in Virginia, what resources are there tend to go to the Dulles Airport extension. Because it is funding by three jurisdictions (the District of Columbia, Maryland, and Virginia) and Congress who has much control over the District, Metro necessarily faces a lot of issues when it comes to control and funding - it is supposed to be run by an interstate compact.
Last time I went up to the Washington Area, I stopped by the Van Dorn Street station to see if anything was in the Van Dorn Street Yard (Norfolk Southern) - I thought that Metro was about the only thing I missed about living up there (Richmond's public transit system is appallingly bad for a city of its size - even living one mile outside of the city limits in an area which 100 years ago had electric rail service (streetcars I believe - may have been interurban) and now has several parks and other attractions the closest bus stop is an half mile away) - driving is a horror and also risky (although often it wouldn't get fast enough to cause much damage in the inevitable accidents).
When I go back to Washington to visit, I'm still going to be riding Metro - and probably still riding in one of the end cars.
penncentral2002 At first, when I saw the photos, I thought that the collision happened in Silver Spring, MD since it looked like Silver Spring where CSX tracks are on each side of the Metro tracks - the Red Line runs on both ends parallel to CSX tracks and often are right next to them (from Union Station to just north of Silver Spring on the east (Wheaton End) and from just north of White Flint to the end of the line at Shady Grove. The Red Line often offers views of rail action especially when approaching Union Station.
Now they are reporting that the train that struck the standing train was under automatic control.
According to Trains Newswire, the operator attempted to stop the train by using the emergency brake.
Johnny
Does the "automatic control" make sure the brakes work?
Computers...they are employed because they are foolproof, don't take coffee and lunch breaks, don't take vacations, don't need health insurance, don't need social security and pension benefits, and don't pick up a pay check. But are they properly fed and cared for? . I have been waiting for such a catastrophic meltdown to see what happens next. Initially here, talk was to look at the train...now I see they are looking at the main computer back at the ranch. I feel we are going into something big...bigger than texting and cell phone misuse. Stay tuned.
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henry6 Computers...they are employed because they are foolproof, don't take coffee and lunch breaks, don't take vacations, don't need health insurance, don't need social security and pension benefits, and don't pick up a pay check. But are they properly fed and cared for? . I have been waiting for such a catastrophic meltdown to see what happens next. Initially here, talk was to look at the train...now I see they are looking at the main computer back at the ranch. I feel we are going into something big...bigger than texting and cell phone misuse. Stay tuned.
henry6,
I think you are on to something.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
I suspect that we're going to find out that the computer lost track (no pun intended) of the train that was rear-ended.
Brian (IA) http://blhanel.rrpicturearchives.net.
blhanel I suspect that we're going to find out that the computer lost track (no pun intended) of the train that was rear-ended.
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?
6. Computer power glich?
7. Is this putting too much reliance on one system without an independent backup?
8. Failure of an IC?
9. GIGO? (garbage in garbage out)
10. How many more possible computer problems can we come up with?
Brian,
Lot more to be sure.
But we humans have become so complacent and reliant on our technology we often never notice.
We wake up to a micro chip beep, our coffee is brewed and ready for us, our TV is on and tuned to the traffic...and we are so just to it being that way we often don't know what to do when it fails.
We have become so dependent on our technology to keep us safe or to correct our mistakes, in spelling, grammar, art and math to name a few, that we have begun to lose those skills.
One of our most human traits, one that sets us above most of the other animals that inhabit this planet is the ability to choose, to make decisions based on intuition and experience, not blind instinct.
Which is why airlines have pilots and co-pilots, trains have engineers and conductors, and transit lines and trolleys have motormen...because the technology does fail, often because the person who programmed the computer failed to include every single scenario that could occur.
Reports have it that the motorman in the trailing put her train in emergency...one would assume because she saw the other train...or maybe she just had that hunch...we will never know because she died...but my point is, had the trains been under a different type of control, or a shared control, this might not have happened.
But my guess is that Metro, and the motorman running the trailing train, simply assumed that because the computer didn't take action nothing was wrong.
Complacency, being so used to the system always working right, will play a large role in this...but the fact she did plug the train while the computer failed to take action confirms that no matter how well thought out and programmed the computer is, there will always be a need for the human interaction and intervention from the cab.
And no, her putting the train into emergency did not prevent the accident, but I bet it saved a lot more lives than we will know.
23 17 46 11
edblysardAnd no, her putting the train into emergency did not prevent the accident, but I bet it saved a lot more lives than we will know.
.
I agree there are a lot more places the computer system could go wrong from the main to the detector system to the on board equipment. But before we totally fry this technology, look at BART and PATCO systems which have had so few glitches over so many more years...plus several European and Asian systems, too.
But the question which comes to my mind is that if you have to put a person onboard to oversee the computer system...like PATCO and Metro here...why not give them control and let the computer system override them instead?
Yes, the 1000 series were built in Winder, GA but the the design was by LT Klauder Consultants and the engineering took place in Chula Vista, CA. The body was constructed with long aluminum extrusions manufactured in Switzerland. The extrusions were "Pop Riveted" together to attain the required height dimensions. The result was a very strong and light weight car. Unfortunately, Rohr aerospace engineers designed for stress rather than deflection witrh the result that tests of the first car revealed that properly fitted doors would hang up with a crush car load. This was corrected with a steel door frame. The car passed all of the specified strength requirements.
Rohr also built the first two orders of the San Fransico Bart system at Chula Vista, CA, using the same construction technique. The spec in this case was by PBQ&D. To the best of my knowledge this series is still running.
At the time all this was going on, I was Engineering & Program Mgr for the Turboliner trains. It was planned to build these in Winder also but when the WMATA cars were delayed, the Turboliners stayed in Chula Vista, for which i was duly greatful. I visited Winder to assess operations there and also provided assistance to the manufacturer of the disk brakes.
Subsequent orders were built by Breda of Pistoia, Italy which had got its feet wet with a contract for ClevelandTransit System light rail cars. I was back at WABCO by this time, managing Passenger and Transit Sales and had the priviledge of negotiating the brake order with Breda.
I concur that NTSB's statement is a CYA effort. Train control and safety systems are supposed to prevent collisions such as this.
Jerry Pier
For any train control system, there are ALWAYS failure modes.
Some of them are there on purpose. For example, there has to be a way to cut the system out in order to move the train in non-controlled territory, such as into and out of a storage yard or shop. Or, to move the train when the system fails. There are usually rules wrapped around who, when, where and how the cut-out can be used.
There can be "false clear" signal indications as well. Even in the "vital relay" world, there can be malfuncitons. I am aware of one where the grease in the signal relay hardened and prevented the armature from dropping. I am aware of another one where a bullet from a hunter's rifle prevented a searchlight signal from dropping back to stop. Similarly, the relay valves in the braking system can stick, be cut out, have a kinked line running to them, etc.
If the Metro uses coded track circuits and on-board cab signalling - well known hardware with a long history - all it would have taken was for the "clear" decoder to stick through some highly improbable combination of failures.
The "computer control" is likely just a "non vital" CTC overlay to keep the trains running. The signal safety system is likely unrelated.
I suppose the automated train wasn't texting at the time...
If there was something on the rails (leaves?), that could have caused a failure of the stopped train to trip the block detectors, giving the second train a green signal into a block that wasn't actually empty.
Jerry Pier Yes, the 1000 series were built in Winder, GA but the the design was by LT Klauder Consultants and the engineering took place in Chula Vista, CA. The body was constructed with long aluminum extrusions manufactured in Switzerland. The extrusions were "Pop Riveted" together to attain the required height dimensions. The result was a very strong and light weight car. Unfortunately, Rohr aerospace engineers designed for stress rather than deflection witrh the result that tests of the first car revealed that properly fitted doors would hang up with a crush car load. This was corrected with a steel door frame. The car passed all of the specified strength requirements.
Thanks for setting me straight! I didn't know LTK was that heavy into transit car structural design.
The cars appear to be very similar to the first batch of Atlanta's MARTA cars. I wonder if they are related.
henry6But the question which comes to my mind is that if you have to put a person onboard to oversee the computer system...like PATCO and Metro here...why not give them control and let the computer system override them instead?
Actually, that's a good point. Unfortunately, it's probably to save money:"We'll pay you minimum wage to open doors and prevent the train from crashing, instead of paying you five times as much to actually control the train."
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ns3010 henry6But the question which comes to my mind is that if you have to put a person onboard to oversee the computer system...like PATCO and Metro here...why not give them control and let the computer system override them instead? Actually, that's a good point. Unfortunately, it's probably to save money:"We'll pay you minimum wage to open doors and prevent the train from crashing, instead of paying you five times as much to actually control the train."
I've seen a few comments regarding the accident as something that could have been prevented by including the Human Being in the control of the train. But "Money" is the ruling element here----as above--
Any argument carried far enough will end up in Semantics--Hartz's law of rhetoric Emerald. Leemer and Southern The route of the Sceptre Express Barry
I just started my blog site...more stuff to come...
http://modeltrainswithmusic.blogspot.ca/
PATCO does exactly what Henry suggests. The operator runs the train manually during off peak periods with the ATC system as a safety backup. This keeps the operators proficient. Only when the need to squeeze out all the variablility of manual operation in order to keep and maintain rush hours schedules and headways do they run in full automatic mode.
(there are no on board computers involved in PATCO's ATC system! It's just cab signals, relays and magnet valves.)
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.
BigJim edblysardAnd no, her putting the train into emergency did not prevent the accident, but I bet it saved a lot more lives than we will know.Maybe she will be the hero of this whole thing. How odd it would be if her name just happened to be Casey Jones.
Given that Mr. Jones was known for disregarding safety rules one would hope not..
I have often seen people get big checks for a job they are not really qualified to do and people who are underpaid forthe job they are doing well. What happens after the individual differences, etc., is a lack of interest or ability in doing better; then crowd mentality sets in and the morale of the group sinks and nobody gives a *** and the work environment worsens more. I am in a business where it is now deemed that anyone can be snagged off the street with just a high school diploma (or not) and be have a career doing what us that have gone on before have had to have college degrees and years of experience for the industry to achieve what it has. Now management is reinventing the wheel but they are leaving out the spokes. Do you think morale is good, Do you think our customers are getting what they think they are getting, what they think they are paying for? No, if you want quality and safety and integrety, you have to hire qualified people, careing people, and pay them a decent wage to do it. Look at what sports figures get. Isn't an employee that can earn a company millions of dollars a year because of his experience, education, and ability, worth more than minimum wage? A baseball, football, basketball, hockey, soccer, tennis, and golf "employees" all get more than that and what do they actually contribute to the society except maybe one spectacular "sports moment" How about the guy who makes sure your car is solid and safe and nobody's gonna get killed because it the car is perfect?
First, older aluminum cars do not seem to be a significant issue here. The damage seems consistent with a moderate rate of speed and the masses of both 6-car trains. If anything, the fact that one car overrode another without more substantial damage suggests a reassuring degree of strength and structural integrity. If the cars had been built much stronger and not overridden one another, I suspect many more passengers in all the cars would have been seriously injured or killed from being "thrown" from their feet or seats.
Secondly, I suspected, as many have written, that the malfunction occurred somewhere in the computer and ato/cab signal systems. As far as detection, even a stopped train draws considerable power for lights and air-conditioning to shunt signal circuits. Furthermore, how could a signal command not be shunted by the lead train in the track circuit that nonetheless had been commanded to slow and stop?
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.
HarveyK400 Furthermore, how could a signal command not be shunted by the lead train in the track circuit that nonetheless had been commanded to slow and stop?
A failure of the wayside track circuit/signal system and/or on board cab signal system creating a "false proceed" is one way. There were 6 in 2008 due to equipment failures in the US.
Take a look! http://safetydata.fra.dot.gov/OfficeofSafety/publicsite/affp/Fpbrowse.aspx
The operator had very little to do with the accident, though there is some question because it appears she had at least 20 seconds to stop the train after seeing the stopped train about 1/4 mile ahead of her.
The evidence is leaning towards failure of wayside equipment to provide control data to the train, or the train failing to acknowledge the control data signals from the wayside equipment.
The arguments from NTSB about crashworthiness of the Rohr cars is total bupkis. The object of the game is to keep trains apart, PERIOD. The speed of this collision would have killed on any train--Rohr, Breda, CAF, Alstom.
Unfortunately we have no telemetry which is very disturbing, not just because the Rohr cars don't have 'black boxes' but also because Central Control should have telemetry transmitted to it by the wayside equipment.
Please, visit the Wikipedia page about the WMATA Metrorail system. I ride it regularly.
http://en.wikipedia.org/wiki/Washington_Metrorail
As an afterthought, I recall reading a long time ago about concerns for cross-talk between tracks with audio-frequency carrier signals. This may be a possible explanation for a false clear signal in the absense of the shunted circuit of the occupied track.
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.
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?
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.
At 45 mph it would take 20 seconds to travel a quarter of a mile with no braking.
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.
- Paul North.
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.
Paul_D_North_JrEven 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?
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?
Deggesty Paul_D_North_JrEven 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.
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
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.
Paul_D_North_JrEven if only a quarter-mile's distance and visibility was available to stop,
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.
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]
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.
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!
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.
Yes, very interesting - to say the least.
Pick one - or more, as appropriate:
Paul_D_North_Jr Yes, very interesting - to say the least. Pick one - or more, as appropriate:
1. Computer control -- OH Boy!! First the obvious. Track detection circuit failed to note train that was run into.
Now lastly could the computer have not allowed the emergency braking to start immediately but had a delay built in? Not likely but------------------
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 ?
"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?
"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.
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.
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.
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.
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.
(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
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.
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.
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.
Back in the 1960s and 1970s, John Kneliing used to love to bash the NYC Transit Authority's operators whenever they had a rear-end collision like this one. Typically, there was a red signal with a 'tripper' that was supposed to automatically dump the air if it was run past - but which was sometimes rendered completely ineffective by being wired/ held down with a bent piece of welding rod.
More often, the signal was manually 'keyed by' so as to allow the following train to 'close in' on a disabled train or 'cripple', or a delayed train still in the station, so as to minimize the delays, etc.
After a series of such accidents, John wrote that the rule was changed to 'Stop and stay stopped, forever' - or at least until a supervisor shows up to take over the controls and run the train [more safely]. I do not recall hearing or reading about many such accidents after that.
So, was there any consistancy anywhere in all of this? There seems to be no real understanding of what a lot of these systems actually do, and if this be the case, then maybe what is needed are some people who really understand these things konking some mgrs heads together to actually make these things work----or rather, make those who are responsible for these things, work....
Another small
BaltACDLocal 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.
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.
Actually, the two modes of operation for both trains are irrelevant since they depend on the same track block circuit signaling. Too much attention has been diverted to the central computer which communicates with the block equipment; but presumably does not interfere with critical safety functions, nor is there a logical rationale to suspect it did.
One of the first reports of the incident said that the stationary train was waiting for a preceding train to clear a platform. It is plausible that the operator of this train asked for permission to go into manual mode and "cutout" the ATP on his train in order to slowly approach the platform while the preceding train was still there. This would not affect the following train at all, but could be the reason the stopped train was in manual mode.
The distance calculation done previously on this forum needs to add a few factors to the overall time frame. I beleive WMATA does not have a magnetic dump valve in their emergency brake system. Instead they rely on application of full service brakes, and remove the load weigh valve and slip slide system when they go into emergency. The FSB rate of 3.0 mph/s/s is correct as the full deceleration. But it takes time for the system to build up that amount of deceleration force.
So a more realistic calculation is to assume two seconds for the operator to react and hit the mushroom, five seconds for the train to remove propulsion and go into braking, and five seconds to build up to full service brake. So at 60 mph (88 fps), the train will travel for seven seconds without any braking effort (616 feet), and then another five seconds as it builds the rate to 3.0. Figure an average deceleration during the build up time of 1.5 mph/s/s. So the train will have slowed 7.5 mph during the five seconds to 51.5 mph. Figure an average speed of 55 mph during that five seconds, so the train will travel another 400 feet. Now you have traveled 1016 feet from the time you hit the mushroom, and are going 51.5 mph, and are decelerating at 3 mph/s/s. That means it will take another 17 seconds to come to a stop. During that time, with an average speed of 25 mph (1/2 of 51.5), you will travel another 680 feet. So figure total distance to a stop is 1696 feet.
Given this was a new driver and her train was in automatic, she may not have realized that she was in trouble until she was a lot closer to the train in front of her then 1696 feet. To hit the mushroom during rush hour, flatten the wheels and disrupt service is not something a new driver would want to do. So she may have hung in there for a while before she hit the brakes.
The real concern in this whole disaster is how a vital track circuit was not shunted by a six car train. That is 24 axles that should have created an occupancy. The fact that this circuit was worked on in the last month points to either a problem that was fixed by turning up the transmit power, or a wiring mistake such as caused the Clapham Junction disaster in England.
I am suprised at how much information is already available to the public from the NTSB, they usually wait a while before they announce anything.
I accept the supplementary and more complete information offered above regarding the time delay for initiation of full service braking -'FSB' - as being better information than any I have, as well as the subsequent calcs. The only qualification I have is my understanding that the speed was 45 MPH, not 60. However, that 45 MPH speed may have been at impact - not at the start of the braking - which would also be consistent with partial braking from 60 MPH at the start of this accident.
The NTSB may be releasing information earlier than usual to reassure a nervous public [ and perhaps to satisfy the obsessive 24-hour news ccycle media]. Keep in mind that there's a huge daily population of users that would be justifiably wondering about the safety now, as well as the NTSB's Congressional masters and budget providers - as well as themselves and their families, friends, relatives, co-workers, and colleagues, etc. So it may be hitting 'closer to home than normal.
Paul_D_North_Jr I accept the supplementary and more complete information offered above regarding the time delay for initiation of full service braking -'FSB' - as being better information than any I have, as well as the subsequent calcs. The only qualification I have is my understanding that the speed was 45 MPH, not 60. However, that 45 MPH speed may have been at impact - not at the start of the braking - which would also be consistent with partial braking from 60 MPH at the start of this accident. The NTSB may be releasing information earlier than usual to reassure a nervous public [ and perhaps to satisfy the obsessive 24-hour news ccycle media]. Keep in mind that there's a huge daily population of users that would be justifiably wondering about the safety now, as well as the NTSB's Congressional masters and budget providers - as well as themselves and their families, friends, relatives, co-workers, and colleagues, etc. So it may be hitting 'closer to home than normal. - Paul North.
edblysard Reports have it that the motorman in the trailing put her train in emergency...one would assume because she saw the other train...or maybe she just had that hunch...we will never know because she died...but my point is, had the trains been under a different type of control, or a shared control, this might not have happened. But my guess is that Metro, and the motorman running the trailing train, simply assumed that because the computer didn't take action nothing was wrong. Complacency, being so used to the system always working right, will play a large role in this...but the fact she did plug the train while the computer failed to take action confirms that no matter how well thought out and programmed the computer is, there will always be a need for the human interaction and intervention from the cab. And no, her putting the train into emergency did not prevent the accident, but I bet it saved a lot more lives than we will know.
CShaveRRedblysard Reports have it that the motorman in the trailing put her train in emergency...one would assume because she saw the other train...or maybe she just had that hunch...we will never know because she died...but my point is, had the trains been under a different type of control, or a shared control, this might not have happened. But my guess is that Metro, and the motorman running the trailing train, simply assumed that because the computer didn't take action nothing was wrong. Complacency, being so used to the system always working right, will play a large role in this...but the fact she did plug the train while the computer failed to take action confirms that no matter how well thought out and programmed the computer is, there will always be a need for the human interaction and intervention from the cab. And no, her putting the train into emergency did not prevent the accident, but I bet it saved a lot more lives than we will know. Ed, back when you posted this, I admired (yet again!) your knack for saying just the right thing. Of course, I agree with you, as would most railroaders who have to walk the walk. And it appears that we're not alone: http://www.cnn.com/2009/US/06/26/dc.train.driver/index.html
http://www.cnn.com/2009/US/06/26/dc.train.driver/index.html
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sftrainsOne of the first reports of the incident said that the stationary train was waiting for a preceding train to clear a platform. It is plausible that the operator of this train asked for permission to go into manual mode and "cutout" the ATP on his train in order to slowly approach the platform while the preceding train was still there. This would not affect the following train at all, but could be the reason the stopped train was in manual mode. ...The real concern in this whole disaster is how a vital track circuit was not shunted by a six car train. That is 24 axles that should have created an occupancy. The fact that this circuit was worked on in the last month points to either a problem that was fixed by turning up the transmit power, or a wiring mistake such as caused the Clapham Junction disaster in England. I am suprised at how much information is already available to the public from the NTSB, they usually wait a while before they announce anything.
You seem to be confusing manual operation of the struck train with either overriding a stop/restrictive or cutting out the cab signal. In this case, my reading of the account was that the operator was manually controlling the train in compliance with the same cab signal system that governs automatic operation. The account given was that the struck train was operated in manual mode with cab signals - although that was not said directly - from the start of the run, not to close up on the train in the station. The train had stopped and was not creeping ahead at restricted speed and overriding the stop signal which can be done with dispatcher consent if necessary. Nor was the struck train operating and moving with the cab signals cut out, which again is allowed under the rules in certain circumstances; but was not the case here. The rules have been explained previously by others; even if not in direct response to the "manual operation" comments.
While the account said the operator of the stopped train was waiting for the preceding train to clear the station, he just as likely was waiting for the cab signal indication to change as for waiting for dispatcher permission to close up and override a stop indication. For what its worth, I see little imperative to defeat safety systems designed to keep trains apart just to save a few seconds.
This type of train control system has worked well with few exceptions for some 30 years. Perhaps WMATA has encountered more exceptions remembered on previous posts than other properties, and may deserve the review that I understand is a normal part of investigations. This technology was developed in response to unacceptable levels of failure in previous systems in the rail transit environment.
Some of you clearly disdain computer and electronic systems; and because it failed in this case, you hint at trashing it out of hand in favor of something else. Just what is your agenda? How many trains have moved safely through the numerous block circuits along their routes since day one? Let the investigation sort out if there was a systemic flaw or whether this was a perfect storm event that can be avoided in the future.
Earlier I wrote of my suspicions with regard to the track circuits. Let me repeat that the system worked for the train that was struck; but not well enough for the following train. A lot of trains passed safely since the circuits were tested previously; so that reduces, but not eliminates, the likelihood of a cause from that source.
I have no information to dispute the ascertion; but 6 seconds seems like an awfully long time for electrically-conrolled air brakes to set up for a subway train. Six seconds would reduce the collision speed by 18 mph.
Comments. I've been watching this on news reports all week.
2 Items that I think the Safety Board(NTSB) will look at.
1. The apparent failure of the signal system to detect the train that was standing still & was struck. One of the pieces I saw in the news was that MTBA(Boston) uses similar equipment from Alsthom(?) and they(MBTA) had a severe failure and warned DC Metro of the failure.
BART(SF Bay Area) during it's 1st few years had no end of troubles with the signal system(Automatic Train Control). Much of it was attributed to the use of a very low voltage(6v or 9v I think) and the overnite build up of condensation(and a very lite layer of corrosion) on the rails
2. The collision itself. The lead car of the moving train(from what I could see of the photos & from published descriptions of witnesses) struck the standing train then rode up of over the last car of that train. According to witnesses the car went up then landed on top of the that car.
I would suspect that cars floor collapsed into the interior. And that would have been the cause of injuries/deaths. From what I've heard of the cars Rohr built for BART(SF Bay Area), most of the train operators believe that in a collision the correct response would be(and I quote) PUSH the emergency stop and thenRUN like hell down the car.
This was what a train operator did about 20-30 years ago when his train hit a maintenance truck (after hours,no passengers) that was hi railing down the wrong track. If I recall correctly that truck went some considerable distance into the BART car. The train operator walked away from the accident, the maintenance crew did not.
Not sure what else to add
Rgds IGN
The "stop and proceed" philosophy in signaling is not new. Most graphic is the "G" signal which indicates that when it is red or most restrictive, train does not have to stop but may proceed under control being able to stop within sight distance knowing that the block ahead may be occupied; this is or was on steep grades and was designed so that there were no problems stalling or restarting on heavy grades and was primarily aimed at freight trains and heavy passenger. Another "stop and proceed" signal was one the DL&W (for one) had at interlockings: four light search light [top red, 2nd yellow, 3rd yellow, bottom green). Red was stop, red over first yellow (diverging route) or yellow was proceed with caution prepared to stop at next signal, red over top yellow over green (divergining route) or top yellow over greet, medium approach, and red over green (diverging route) or green, clear or proceed. There also was a red over the lower yellow which allowed a train into an occupied block at restricted speed prepared to stop short of a proceeding train or other obstruction. I saw this used frequently during rush hours to keep traffic moving through interlockings so as not to block station platforms and also to return to a train when setting out or picking up cars from sidings.
Let me add some fog to this speculation.
When the DC Metro opened for the 1976 Bi-Centennial, the best mico-computers ran on a 16 bit, 3MHz chip. That orignal control system must be long gone. In the computer world, replacement chips are a problem after 20 years.
Alstrom of France runs the TGV trains at 3 times the speed of the DC Metro, they should know what they are doing.
The talk in this column is of a Block / Signal System. Was this a Block / Signal System? or a Time Spaced / Headway Timing System? (Train speed / Train separation / Passenger waiting time, governs Train position).
In "Automatic Mode", the operator does not control the speed. in DC, Boston, the operator hits a start button and the computer brings the subway train up to the proper speed and stops at the next station.
Want to speculate: PURE SPECULATION
Train 1 is in the station, train 2 was stopped and holding, it went Manual (assume with permission) to pull up behind train1 on what we would call a limited approach (15 mph or less, a speed that lets you stop in half the distance to any visble obstruction) . When train 2 pulled forward, the computer failed to recognize two trains in one block or read it as one long train. The Stop for train 3 was lifted and it accelerated to appproach speed. Train 3 hits train 2.
Try taking off the "index.html" part.
http://www.cnn.com/2009/US/06/26/dc.train.driver/
DMUinCTThe talk in this column is of a Block / Signal System. Was this a Block / Signal System? or a Time Spaced / Headway Timing System? (Train speed / Train separation / Passenger waiting time, governs Train position).
Metro is fixed blocks, I believe. Is there any transit operation that uses floating blocks in regular operation? There's been a lot of talk, but I don't thing anyone has implemented.
Fixed blocks are fixed blocks. I believe since the enforcement is reactive, they a have to keep an extra block between trains. It is unlikely that they give trains permission to cut out the ATC very often - certainly not during regular operations without some sort of equipment failure. Creeping up on train ahead ala frt railroading would not be part of regular operations.
This is sounding more and more like a mal-operating track circuit caused a false clear indication.
Adding to Don's post.
If this boils down to a lost occupancy and resultant false-clear, there's nothing particularly magical about the cause of the lost occupancy, or designing and implementing a solution. This is plain-old signal engineering. I don't see any reason to fret about the evils of computers leading us to our doom, unless you happen to consider a Saxby & Farmer lever interlocker of 1890 to be a computer (which it sort of was).
I don't know of any floating-block systems in the U.S. in revenue service. The NYC Canarsie Line CBTC system entered revenue service in 2006/2007, but I have seen nothing about floating block being implemented there yet.
There is so much more detail coming out every day that I've decided to defer an opinion for now. Sliding blocks is an interesting concept!!
A new finding came out, too. The operator of the "struck" train had earlier gone into manual mode because his train didn't stop for a train in front of HIM. Plus the test train the NTSB ran did not indicate an occupied block, prompting a system-wide inspection of all wayside equipment. There are all kinds of Metro alerts for single-tracking throughout the system this weekend.
The DC Metro's Wayside signals are very simplistic: essentially, the wayside aspects are only Stop, Go, and the equivalent of "Go Carefully." The Metro is totally dependent on in-cab and telemetry. The telemetry appears to be the failure. It's very sad and very bad. The operator of the "struck" train should be commended. The operator of the "striking" train could not do anything to avoid the tragedy. Very sad.
[QUOTE:sftrains]I am suprised at how much information is already available to the public from the NTSB, they usually wait a while before they announce anything.[/QUOTE]
The DC Metro does attempt a certain level of transparency. They are a little miffed by the NTSB's rush to judgment in other matters and are more than happy to facilitate the release of details either through WMATA itself or the NTSB. WMATA is very interested in forcing the issue of dedicated funding, which they inexpicably do not have. This incident will be the catalyst for dedicated funding they so desperately need.
narig01 ...I would suspect that cars floor collapsed into the interior. And that would have been the cause of injuries/deaths. From what I've heard of the cars Rohr built for BART(SF Bay Area), most of the train operators believe that in a collision the correct response would be(and I quote) PUSH the emergency stop and thenRUN like hell down the car....
It's been a few days since the pictures were posted. I notice then that, contrary to your "suspicion," the overriding car was pretty much piggy-back atop the bottom car with little collapsing. This was alluded to in my comment regarding the apparent structural integrity despite concerns for the age of the cars.
Of anybody, RMW might have the best feel for whether there is a possibility that a stray clear signal may have leaked from the adjacent track.
Given that the system lost the struck train, it seems the same restricting signal that brought it to a stop, not a clear, would also command its follower to reduce speed and stop at roughly the same location.
DMUinCTTrain 1 is in the station, train 2 was stopped and holding, it went Manual (assume with permission) to pull up behind train1 on what we would call a limited approach (15 mph or less, a speed that lets you stop in half the distance to any visble obstruction) . When train 2 pulled forward, the computer failed to recognize two trains in one block or read it as one long train. The Stop for train 3 was lifted and it accelerated to appproach speed. Train 3 hits train 2.
Maybe I missed an update of confirmation, but there is a lot of ongoing conjecture that the struck train had moved into the block occupied the the train at the station. All that was reported is that the operator was waiting for the train in the station to clear. The number of trains in the station block would be immaterial since the circuit was, and would continue to be, shunted. This would not "clear" the preceding block, only continue the restricting (approach) signal command.
Railwayman,
It was not my intent to present all of this in a "man vs. Machine", or the "us vs. them" Terminator scenario...believe me, I fully embrace the use of computers and the associated systems they require to function.
If computers are leading us to our doom, then we are already doomed, we have relied on them for so many years that I doubt today's form of society could survive without them...look at how we are communicating right now.
My car in fact, couldn't run without the computer it employs...the thing doesn't even have a throttle cable, the only manual functions you can perform without computer aid is opening the door and steering the car, and the computer has a hand in both that now that I think about it.
My point was the complacency that is slowly creeping into our industrial application of computers...we, the end users, tend to forget that the computer can only follow the program it is running, and that program was written by a human(s) who can and often do make mistakes.
My line of thinking was more along the lines of a system failure, not a computer failure...one where a component failed and the "what if this happens" part of the safety program didn't catch it because it was not programmed to catch that one specific failure.
And by "system", I mean the entire operating system, from the operating practices that allowed the train that was struck to creep up behind another train and occupy the same block to the track circuit design that didn't, for what ever reason, alert the computer of the conflict with the following train.
We have become so used to things working, and working in a manner we think of as "right" that we tend to forget this stuff is a machine, and machines and mechanical components do fail.
We also tend to forget that computers can only follow their program, we act as if the computer can "think" for itself, and if no one ever anticipated this one specific scenario, then no one wrote a piece of programming to deal with it.
My thoughts are that the practice of allowing two trains on a commuter line to get that close to each other, and then giving control of one of these trains to a computer is operationally and fundamentally unsafe...the motormen should, in my opinion, have had a way to communicate verbally to each other, and had a degree of control of their respective trains.
Once manual control was given to the standing train, the system should have given some form of signal to all following trains to "go looking", some version of restricted speed, and the capability of the following train(s) to go to manual operation and comply with the restricted signal.
It didn't, it allowed one train to operate differently that all the other trains, and that one train, because of the system design and operation practices, "disappeared".
If you are going to allow one train in an automated system to function manually, you should give a degree of control to all following trains till all the trains in the system are back running on automatic.
From what I have read, the NTSB parked a train in the same spot, and the system did the same thing again, it allowed a following train to proceed, and would have again allowed the following train to strike the standing train.
While a lot of folks seem intent to find a single fault causing this accident, in that they want to blame a computer, or a signal, it is my contention that the "fault" is in both the programming that allows these trains to get that close, and the operation practice of allowing this to occur under both manual and computer control in the first place.
I think it was a system and operational practice failure combined...the "manual" and operational failsafe practices we routinely use in freight railroading were not there, add in the fact that there was a combined manual and computer controlled operation allowed simply presented a situation that no one had anticipated, and no one had written a program into the automated side of the system to stop the trailing train.
Skipping in and out of manual and automatic operations seems to have overwhelmed the operational practice's safety system.
I would bet that once the NTSB finishes its investigation, they will find the computer did exactly what it was programmed to do...it functioned as intended...and I would bet they recommend that the practice of allowing one train in an automated system to go manual and creep up to occupy the same block as an automated train should be prohibited.
Maybe what I am pointing at is simply this...
If the motorman in the standing train had been required by rule to announce over the radio to all following trains that he was sitting right behind a train at a given point, and that all following trains should come looking, then the odds of this happening would have gone way down.
He wasn't required to do that, we instead relied on a system that, up to this point, had functioned just as intended.
But a simple radio call, a basic freight railroading safety practice, would have prevented the accident.
So why was this not part of the operational practice?
Don't simply blame the computer, or a track circuit design, blame too the operational practice that allowed the combined system, as a whole, to fail.
You and I both know that most operational practice and safety rules are truly written in blood.
HarveyK400 Of anybody, RMW might have the best feel for whether there is a possibility that a stray clear signal may have leaked from the adjacent track. Given that the system lost the struck train, it seems the same restricting signal that brought it to a stop, not a clear, would also command its follower to reduce speed and stop at roughly the same location.
I know a good bit about cab signal equipment - at least enought to get myself in trouble!
The struck train was stopped waiting for the train ahead to clear the station. I don't think it crept into the same block as the train in the station, either. In fact, there was likely an empty block between the stopped train and the train in the station - needed because the Automatic Train Protection system (ATP - cab signals with reactive braking) ) is reactive. Operating in manual mode does not override the Automatic Train Protection system. The ATP can be cutout but It is not normal operating procedure to allow this on the road unless there is an equipment failure that keeps the train or train ahead from moving at all and then operation is limited to 15 mph. There has been not mention of any ATP systems cut out in anything I read.
The block that the stopped train stopped in apparently did not register occupancy. To the signal system, this has the same effect as if the train ceased to exist. The following train would get cab signal aspects as if it was following the train in the station. The block with the train in the station would have "no code" behind it to the next block boundary. The following block would have a "stop code" in it. The block with the stopped train would have "approach" in it. The block behind that (with the striking train in it) would have "clear" in it. (Assuming system is built around three aspects plus stop like the PATCO line in Phila/NJ oops. CRS disease. PATCO has 4 aspects plus stop, but they use them for more than just train separation.)
It is extremely unlikely that the "clear" track code leaked from the adjacent rails. More likely, but still way out there in the odds would be that the cab signal receiver bars picked up the code on the adjacent track. The on board cab signal system would have to be so far out of whack for this to occur that it would have encoutered cab signal flips all over the place prior to the crash or the failure of the equipment on the car would have to have occurred at just the right moment.
But, since they've already found the "smoking gun" - a track circuit that doesn't register occupancy of trains - no other failure mode needs to be added on to create a plausible explanation for the crash.
Except that the track circuits and on board cab signal system may have microprocessors in them, no computer failure, in the classical sense, would have been involved here. Metro's computer automation is all about managing the flow of trains on the network within the bounds of the ATP (cab signal with reactive braking) system. Think of this as driving your car at 30 mph and braking gently up to the red light ahead instead of zooming up at 50 mph and braking hard. It smooths the ride and paces the traffic, but it can't make the red light green.
The term "telemetry" has been kicked around. In the ATP system, the only "data" from the wayside to the train is the coded cab signal in the rails that the train picks up inductively. It's a very crude modulated audio frequency signal - 100 year old technology. Calling this telemetry is like calling the NYC 999 and the Empire State Express a "High Speed Rail trainset".
oltmanndBut, since they've already found the "smoking gun" - a track circuit that doesn't register occupancy of trains - no other failure mode needs to be added on to create a plausible explanation for the crash.
Don,
From the discovery of a track circuit that does not register trains, how likely is it to find a specific fault that caused this? Would the fault generally have to be a failed electrical connection or switch contact? What are some of the specific possibilities that could constitute that fault?
edblysard [snips] Maybe what I am pointing at is simply this... If the motorman in the standing train had been required by rule to announce over the radio to all following trains that he was sitting right behind a train at a given point, and that all following trains should come looking, then the odds of this happening would have gone way down. [emphasis added - PDN.] He wasn't required to do that, we instead relied on a system that, up to this point, had functioned just as intended. But a simple radio call, a basic freight railroading safety practice, would have prevented the accident. [snip] You and I both know that most operational practice and safety rules are truly written in blood.
If the motorman in the standing train had been required by rule to announce over the radio to all following trains that he was sitting right behind a train at a given point, and that all following trains should come looking, then the odds of this happening would have gone way down. [emphasis added - PDN.]
[snip] You and I both know that most operational practice and safety rules are truly written in blood.
From the quote above, my understanding is that edblysard isn't proposing that all stops be broadcast - only those stops where a 2nd train comes up and stops behind another one would be required to be radioed to following trains.
So unless this is a common occurrence, there wouldn't be a lot of radio clutter resulting from this.
What I'm not understanding [yet] is how this precaution really promotes safety - other than to verbally alert following trains that there's severe congestion on the line ahead and that they, too, should be prepared to likely have to stop, because now there are at least 2 trains ahead of them that will have to clear out of the way. But this procedure is essentially redundant to a properly operating signal system - the entire length of all of the stopped trains should be causing a red signal at the entrance to any rearward block which is even partially occupied by a train - or even a single car. So the following trains ought to be seeing Yellow/ restricting in advance of the Red anyway. Likewise, even though the 2nd stopped train may be also occupying a part of a block that the 1st stopped train is in - I don't see how that diminishes safety. If any entering block signal is Red, then there could be a train anyplace in that block - at the far end, or just inside the Red signal - unless someone is assuming that the Red is caused only by a train at the far end, and that's an assumption that is not supposed to be made [it's like 'running on Yellows'].
Bucyrus oltmanndBut, since they've already found the "smoking gun" - a track circuit that doesn't register occupancy of trains - no other failure mode needs to be added on to create a plausible explanation for the crash. Don, From the discovery of a track circuit that does not register trains, how likely is it to find a specific fault that caused this? Would the fault generally have to be a failed electrical connection or switch contact? What are some of the specific possibilities that could constitute that fault?
Since it's still not working, they ought to be able to determine the cause. They probabilities of specific failure mechanism is way out of my depth. Looking at the "False Clear" database on the FRA website, it appears that more are human caused than equipment failure, though.
oltmannd [snip] - 100 year old technology. Calling this telemetry is like calling the NYC 999 and the Empire State Express a "High Speed Rail trainset".
There's my dose of humor for the day - thanks.
And -
oltmannd I know a good bit about cab signal equipment - at least enought to get myself in trouble!
Now here's a man with integrity. 'A man's got to know his limitations' - nothing wrong with stating that - too many are afraid to admit that they don't 'know-it-all'.
[Me, too - except that I'd get in trouble from how little I know about cab signals.]
zugmann There would be so much talk on the radio that it would be useless.
I agree that the "radio" solution wouldn't be good. There would be so much radio traffic, operators would just tune it out - even if it was only done when one train was stopped behind another. This is a very regular occurance on heavy rail transit systems.
If they are tuning all the chatter that doesn't pertain to their train, they're likey to miss something that is directed at them.
Paul_D_North_Jr If any entering block signal is Red, then there could be a train anyplace in that block - at the far end, or just inside the Red signal - unless someone is assuming that the Red is caused only by a train at the far end, and that's an assumption that is not supposed to be made [it's like 'running on Yellows'].
Which is why transit operations usually keep and extra block between trains.
If you run by a stop and there is a train in that block, applying the brakes at that point might be too late.
Regarding edblysard's long post, the comment that I have to make about Metro's operations is that the trains can and do "creep up" to the next train. The headways are very short. At stations you can see the following train about a platform's length behind you. The trains stop in tunnels and creep forward 10 yards or so at a time several times. It happens every day.
Regarding blocks, it sure appears to me that Metro allows more than one train in a block in the course of normal revenue service, and those trains are both computer-controlled and manually-controlled.
Heck, before the 1996 accident, the operators weren't even allowed to drive the trains manually because of excessive flat spots. The system was running for 20 years by that time.
There are sensors between the rails every few yards. Every description I have ever read about the DC Metro is that the central control center (in DC) knows where every train is and that's due to these embedded sensors.
Hi, zugmann, DC Metro's rush-hour timetable states that trains arrive at stations less than 2 minutes apart. I ride the DC Metro and at Metro Center it's well under 2 minutes between trains.
aegrotatioRegarding blocks, it sure appears to me that Metro allows more than one train in a block in the course of normal revenue service, and those trains are both computer-controlled and manually-controlled.
I'd bet that blocks are pretty short, some <1000 feet, which gets pretty close to a platform length.
The control center may know where every train is but that has nothing to do with the ATP system - which is the safety system. The control center is not part of the safety system.
zugmannYou can't compare a freight operation to a mass transit operation running every 7 minutes. There would be so much talk on the radio that it would be useless. There should be no need to talk every time a train stops. That is why we have signals. Yes signals can fail, but how many precautions can you justifiably take for an extreme event (all the while being able to move people efficiently)? What's next? Hire rear flagmen for the metro? The radio could fail as well. Better send someone out with fusees and torpedos. Even in freight ops we don't announce to the world every time we stop for a signal. That is why we have a signal system. If there's a train stopped ahead, we get a restricting and proceed prepared to stop in half the distance. No radio needed.
I wasn't trying to snap at anyone. But there's a difference b/t a section of busy class-1 mainline with a dozen or so trains on it, and a metro line at rush hour with trains spaced every 2 minutes. (2 minutes...wow). We do sometimes tell trains pulling in behind us where exactly we are and what our lenght is, but that info isn't 100% neccisary as that train behind us must be following restricted speed rules.
When you're as vusy as metro, I doubt it would be very safe to have every train announce every time tehy pause for a few seconds until they can occupy the next block. Unless something goes wrong, they shouldn't be sitting there very long.
But that's my opinion. Take it for the electrons it's written with.
I'm not seeing much solid information here. First, read the July 1 NTSB report. The NTSB has already determined that it's a track circuit problem. But they're still not sure what failed.
For background, read one of the previous NTSB reports on Metro collisions. The signaling system is classic General Railroad Signal relay-based fixed blocks with audio-frequency track circuits. That's century-old technology, and Metro is still using the original 1970s trackside systems. There are no computers in the basic train protection system.
The NTSB currently suspects problems with an impedance bond between two blocks. (An impedance bond passes traction power but not signal info.) This puzzles me. An impedance bond that fails should not result in a false clear indication. A short between adjacent blocks should result in a train in either block appearing to be present in both. An open should result in a false indication of train presence. Adjacent blocks should use different audio frequencies, so leakage isn't normally a problem. How did this fail?
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