Derailment at Farragut North a safety system success

Transit

Derailment at Farragut North a safety system success

by Matt Johnson • February 12, 2010 11:27 pm

This morning's commute was marred not only by the snow drifts spread across the region, but also by a minor derailment on the Red Line at Farragut North.

While there was some confusion in initial reports, some things have become clear about the accident. The derailment itself was caused by a safety device known as a "derailer," which prevented the train from entering a track potentially occupied by another train.

The pocket track at Silver Spring has a similar configuration as at Farragut North.

This incident occurred at the northern end of the pocket track immediately north of the Farragut North station. The train that derailed was carrying about 350 passengers in the direction of Shady Grove. Three minor injuries were reported, and one passenger was transported to the hospital.

Because the accident occurred in the pocket track, the train did not foul either of the main tracks, and a few trains passed by in both directions before the station was closed. Passengers were eventually rescued by being moved to the rear four cars, which returned to Farragut North.

The train was bound for White Flint station. White Flint was to be the terminal because Twinbrook, Rockville, and Shady Grove remained closed due to snow accumulation on the tracks. After stopping at Farragut North to allow passengers to board and alight, the train began to head north toward Dupont Circle. Immediately north of the Farragut North platform, there is a pocket track.

Click to enlarge.

This pocket track is typically used to store trains or allow them to turn back in the direction from which they came. In some cases it is used to allow trains to switch between the inbound and outbound track.

For some reason, the switch was set to allow the northbound train onto the pocket track (at "A" in the diagram). It is unclear at this time why the switch sent the train into the pocket. However, the operator continued traveling toward Dupont Circle at a low rate of speed. This low speed would have been enforced by the Automatic Train Control (ATC) system.

The pocket track is about 600 feet long, the same length as a Metro platform. At the northern end of the pocket (at "C" on the diagram), is another switch. This switch enables trains in the pocket to switch to Track 1 or Track 2. At this point there is a signal and derailer. Since the derailer was engaged, the signal should have been red - assuming there were no mechanical or electrical problems with the device. The train operator should have been able to see the red signal when the train entered the pocket (at "B"), at least 600 feet away.

Now, the signal at "C" would only show a clear to proceed aspect if several conditions were met: The switch at "C" is set to the right, the switch at "D" is set for the pocket turnout, and the track immediately north of "D" is clear. Or, the switch at "C" is set to the left, the switch at "E" is set for the pocket turnout, and the track immediately north of "E" is clear.

Otherwise, the signal would show a red aspect and the derailer would be engaged.

The derailer works by literally derailing the train. Basically, if the switch is set in a manner which will direct the train into danger, the derailer is engaged. It is automatically operated by the signal system and, when engaged, is placed flush against one of the running rails.

It essentially acts as a ramp for one of the wheels, lifting it up to the level of the rail. It then channels that wheel toward the outside of the track, which causes the wheel truck to drop so that one wheel is off the trackbed and the other wheel is in between the running rails. This creates additional friction, and should stop a train even if braking power has been lost.

Of course, derailers can fail. One of the most tragic cases occurred on September 15, 1958 when a commuter train bound for the ferries to New York City ran off the end of an open drawbridge. The accident killed 48, including Kurt Vonnegut's brother-in-law. He references this accident in his works.

As the train approached the CRRNJ Newark Bay Lift Bridge, it ran through three red signals and hit a derailer 450 feet before the bridge. Despite being derailed, the two locomotives and three passenger cars skidded off into the bay.

In today's derailment, however, the derailer worked as intended. In fact, not only did the derailer prevent a collision or damage to misaligned switches, it also prevented the train from fouling either main track. However, while this event saw the safety system avert potential disaster, it is not clear why a potentially dangerous situation was allowed to progress so far. Many questions remain.

All of Metro's riders can hope that the root cause will quickly be determined so that future instances can be prevented.

34 comments — Share	— tags: derailment, Metro safety, WMATA

How has Metro responded to NTSB recommendations? (Oct 22, 2009)
The Price of Safety, part 2: Recent derailments expose problems (Oct 14, 2009)
Metro's buffet line effect: Proceed directly to dessert for best results (Sep 16, 2009)
A look at Metro's safety systems (Jun 24, 2009)
Metro actually works (sometimes) (Nov 19, 2007)

Comments

Excellent research and diagrams, Matt. Congrats on your WUSA appearance as well.

Now why was the train running on the pocket track in the first place?

by Reza on Feb 13, 2010 4:48 am

Are trains carrying passengers even allowed on pocket tracks?

by KenF on Feb 13, 2010 8:21 am

Your picture describing the location of the derailer is wrong. The derailer is located before the turnout points at C in your diagram of the Farragut North pocket track.

I made a mental note of location of the derailer at the north end of the Farragut North pocket track when I walked those tunnels back in the early 1970 during construction.

by Sand Box John on Feb 13, 2010 8:40 am

Matt, you need to consult for the local media. Yesterday's news reporting on this incident was abysmal, and I'm not even sure the Metro spokespeople knew what they were talking about. Explaining things clearly and concisely will do a lot to help the public understand what happened. Instead, all we heard, from "man in the street" interviews, about was how confused the situation was and that people were "trapped" underground. Hardly re-assuring on a day when the region's entire transportation network was in disarray.

by Paul on Feb 13, 2010 9:13 am

Thanks for the explanation, Matt. I'm with @Reza now...why was the train on the pocket track in the first place? Hmmm..

by Matt Glazewski on Feb 13, 2010 9:16 am

Drawing of derailer from WMATA Signal Maintainers Manual

by Sand Box John on Feb 13, 2010 10:07 am

@Sand Box John:
As usual, you are correct. I didn't mean for the diagram to be fine-scaled. The derailment would have occurred as the train passed the signal (shown as a keyhole shape on the diagram). I actually intended "C" to mean the switch points. I apologize if that was unclear.

by Matt Johnson on Feb 13, 2010 11:06 am

Matt:
Your diagram is fine, it is the location red circle in the your photograph of the Silver Spring pocket track that is wrong. The red circle should be just beyond the turnout points of the pocket track.

by Sand Box John on Feb 13, 2010 11:25 am

Well, the derailer did its job. The question is why was it even necessary? Why was that train on the pocket track to begin with?

by Alex B. on Feb 13, 2010 12:01 pm

I was on the train that derailed. When I boarded the train at Union Station, the destination displayed on the electronic signboard was 'Farragut'. I had to go further along, so I expected to have to exit there and wait for another train in the same direction. At Farragut North, the operator announced that the train was going to White Flint. This suited me, so I stayed on and of course, we derailed a few hundred yards north of there.

I had my earphones on for most of the ride, so it's possible that she was announcing that it was going to White Flint all along, but I'm certain that the signboard at Union Station said Farragut.

I didn't think much of this until I started reading about us being on the pocket track in the reports. Since it appears that somebody in the control center had put the train on the pocket track, could it be that they still thought it was turning around? Of course, only an investigation will tell if the change in destinations had anything to do with it. This seems apropos to me, though.

I'm certainly glad the derailer worked and I think the evacuation was handled reasonably well. But yes, I'd certainly like to know what was at the root of this.

by HM on Feb 13, 2010 2:29 pm

I agree that a route must have already been set by the system for the train to enter the pocket track at Farragut North, based on HM's observations and comments. It's possible that the onboard destination code was faulty (or a corresponding decoder in the field or downtown) and the train was automatically routed there. The operator and/or the controller downtown might not have noticed the indication. Or, perhaps neither of them were alert enough to realize the destination indication of Farragut North meant the train was headed into the pocket.

It seems to me it was a big surprise to the controller(s) and the operator. Because it is not a typical, normal move; I suspect they were not familiar with Farragut North operations concerning the Derail switch (note from the manual posted by Sand Box John, the proper term for this switch is a Derail and not a derailer (even though that is its function).

by atc1worker on Feb 13, 2010 3:14 pm

Great post. Commenting so I can subscribe to the comments; enjoying the discussion.

by JMS on Feb 13, 2010 4:46 pm

@KenF
I have been on the pocket track at West Falls church a few times before. Often due to scheduling or single tracking, this is used for revenue trains.

by Joshua Davis on Feb 13, 2010 8:08 pm

HM:
If what you describe is true, then the interlocking route controls functioned as designed sending him into the pocket track. If the operator assuming he was going to White Flint, he should have check the destination code display to verify that his final destination was in fact some point beyond Farragut North, or at least check the iron to make sure he was not going to be routed into the pocket track. It also appears that the hardware in the Farragut North A02 train control room has not been upgraded to display a flashing aspect for diverging route turnout setting.

There is no destination code for White Flint, unless WMATA has modified the destination code table within the last 5 years.

atc1worker:
You are quit correct. I used the word 'deraler' to maintain consistency with what the media was calling the device.

by Sand Box John on Feb 14, 2010 1:06 am

I don't have the time, sorry to say, to wade through all what happened. The only thing I heard was that the train was on the wrong track and hence the safety mechanism was triggered. The safety mechanism was a good thing. But the operator being on the wrong track?

Do I have it right or wrong?

by Jazzy on Feb 14, 2010 7:31 am

@Jazzy: That's pretty much it, the train was in the wrong place and was about to go into a worse place. A safety feature derailed the train rather than let that happen.

by Michael Perkins on Feb 14, 2010 8:54 am

This is some serious "S" I hate to say. And as "no duh" as this may seem, it just goes to show how critical (now, yesterday) it is to REORIENT Metro and its priorities to safety. Safety has to be the sun around which everything else revolves. No other words should be coming out of Metro spokesmen's mouths that do not revolve around the fundamental concept of safety first.

No duh, I know.

by Jazzy on Feb 14, 2010 10:20 am

@Sand Box John: I believe the tracks north of Medical Center had just been cleared and they'd started running trains up to White Flint. I remember seeing a train coming 7 minutes later destined for WF on the signboard. That's the one I expected to have to transfer to after disembarking at Farragut North.

by HM on Feb 14, 2010 11:53 am

Your picture needs revising - the red circle is highlighting the switch points. A derail cannot be placed within a switch, it would be further back between the equilateral turnout and the mainline turnout.

by Steve on Feb 15, 2010 1:11 pm

Agreed. There is no derail in the picture with the red circle (not even where a derail would be if one existed in the pocket track photographed).

Otherwise an excellent article on the incident. Two questions for WMATA to answer:
1) Why was the train in the pocket? (Misrouted?)
2) Why didn't their operator STOP for red? (Not paying attention.)

by justalurker66 on Feb 15, 2010 6:35 pm

justalurker66:
From the description of event, it sounds to my like the train was in fact not misrouted into the pocket. From what I can piece together the train operator was informed by radio at some point west of Gallery Place that his train would change it's destination from Farragut North to White Flint. The OOC supervisor did not at the same time send a command to wayside to change the destination of the train from Farragut North to White Flint. The train berthed at the Farragut North with a Farragut North destination. Local train control properly set the interlocking to short turn the train in the pocket track. What happened after that is what needs to be investigated.

by Sand Box John on Feb 15, 2010 8:12 pm

What I still don't get is this: why is it necessary to derail the train? Can't the automated systems just apply the brakes? It seems as if that's what the system does when, say, a train approaches another train too closely.

I guess a derailer makes absolutely, positively sure that the train doesn't move. But that damage to the train is at least six figures, probably seven. Not to mention passenger injuries (not too severe in this case, but could have been worse).

So why derailing? Why not something less severe?

by Tim on Feb 16, 2010 8:48 am

@Tim, was damage to the train really six or seven figures? Seven figures would be almost a total loss.

This was probably five figures, and mostly limited to maintenance inspections of the railcar and track structures to look for damage. Much better than repairing damage to switches or the possibility of the collision.

It's also possible that the reason the train is passing through the red signal is due to a brake or traction failure. If that happens, derailing is a positive means of ensuring the train doesn't move.

Somebody help out on this one.

by Michael Perkins on Feb 16, 2010 9:05 am

Tim, the derailer is the absolute last resort physical failsafe. As Michael notes, it's there to prevent accidents like this one from turning even bigger, but also to stop runaway or out of control trains from entering the other track.

There's no doubt that the derailer never should have been necessary here, but that's because something obviously went wrong prior to that point - either the operator went through a red signal or there was a snafu in the control center - but that's where the fault lies, not with the derailer.

by Alex B. on Feb 16, 2010 9:16 am

The doublethink by the authors of this blog has reached a new high. They're so desperate to defended their beloved mass transit that they'll equivocate over anything...

by MPC on Feb 16, 2010 9:25 am

@Michael: Honestly, I just assumed six or seven figures, because from what I've seen about damage to these cars (e.g. the West Falls Church yard collision), repairs are damned expensive. My point is mainly that if conditions permitted (enough space, train was slow enough, etc.), it would have be better, by many means, to not derail the train.

@Alex B: That's definitely a good point; derailing is a last resort. But when it comes to safety systems, it seems as if the space between second-to-last resort and last resort is pretty big. In this case, the second-to-last resort was a red signal (admittedly, a long series of red signals), then the last resort was derailment. The short length of track between the pocket and the main line may have necessitated this, but I'm not completely sure.

by Tim on Feb 16, 2010 9:28 am

@Tim,

The point of the derailer is to be the last resort. I'm not sure what you're arguing for. If you think something else less extreme should have been done first, well that's obvious - and it was in place (the red signal). The derailer is a crude and effective measure to stop a train. Think of it like an airbag in a car - it's designed to prevent an even bigger problem, not to stop the problem from occurring in the first place.

@MPC,

What equivocation? I see explanations of what happened. I also fail to see what the narrative of this event has to do with larger issues of rapid transit. Come on, man - I know you can do better than this.

by Alex B. on Feb 16, 2010 9:46 am

@Tim, Michael Perkins, Alex B.
The pocket track is about 600 feet long, the length of an 8-car train. The ATC system would enforce a very low speed because the train is in a short block with turnouts at each end.

However, if the train cannot stop at the end for any reason, there's no room for error. A derailer ensures that a train will stop before endangering other trains. The ATC system can stop a train (by enforcing a zero-speed command), but that takes time. Since the time/distance to stop a train varies based on speed and conditions, the derailer is necessary in situations where any violation presents a danger.

On mainline tracks, the ATC system is supposed to keep well over one whole train length clear behind each train. So following trains have plenty of time to stop and a derailer is not essential.

Michael is correct about other system failures too. The Woodley Park accident shows that the ATC system won't stop trains in manual from rolling backwards. While Metro's pocket tracks are probably all level, there is at least the concern that rollback or brake failure could endanger trains on other tracks. The derailer will protect against that absolutely (unless the switch is properly set, but then the ATC system would have the tracks ahead clear).

As for the cost of repairs, I think Michael is probably right. I doubt expenses will go over 5 figures. These railcars are not totalled. At worst they would need a new set of trucks.

The WFC Yard collision was a very different scenario. Consider this: You're driving down the freeway at 60 mph, and you hit a stopped train. Your car, and probably the one you hit will be totalled. This is the case for the Fort Totten accident. Same scenario, except at 25 mph. At least one of the cars is going to be totalled or significantly damaged, especially if it was a 1975 model, which is the case with WFC.

Now imagine you just took a corner a litte tight and sideswiped a parked car. That's a little more analagous to Friday's incident.

Not every railcar accident totals the vehicle, but when they're totalled, they cost a lot.

And Alex B. is correct. At least one thing went wrong prior to the train striking the derailer. That's what the true cause is, and that issue will need to be fixed.

by Matt Johnson on Feb 16, 2010 9:51 am

Yeah, all of the pocket tracks I can think of are fairly level, but remember that immediately north of this particular track, the rails descend into the Dupont Circle station. If the train in question had lost its brakes and wasn't derailed, it could have gained speed rolling downhill on the inbound track.

by Alex B. on Feb 16, 2010 10:02 am

The intended purpose of the Derail is to prevent "rolling stock" in the pocket track from encroaching on the mainline during revenue train operations. The pocket track may need to be used as a storage track for heavy rail maintenance equipment, for example. Depending on moveable-point switch positions and signals and presence of trains in the area, the system is designed to set the Derail on top of the rail in case gravity and weight of a possible wayward "rolling stock" work vehicle were to roll onto mainline during normal revenue operations.

A revenue train route to the pocket at Farragut North would typically be reserved for unusual circumstances; for instance, using Farragut North as a temporary terminal point due to an emergency or a train failure where the controllers would need to move it temporarily into the pocket to get it off the mainline thereby minimizing disruption of normal operations.

I know for sure there is another Derail in the pocket on the east side of West Falls Church station. West Falls Church is a critical interlocking, linking the West Falls Church rail yard to the mainline, and is also near the site of the future Dulles rail connector.

As long as signals are clear in front of a train moving out of the pocket, the Derail will be disengaged (off the rail). The two questions posed by justalurker66 1- why was the train directed into the pocket (faulty destination code? bad idea?) and 2- why the operator ran a red signal - definitely happened - (had she received permission from Central to do so?) indeed need to be answered to get to the bottom of why the incident occured.

by atc1worker on Feb 16, 2010 10:03 am

@MPC:
Doublethink: Thought marked by the acceptance of gross contradictions and falsehoods, especially when used as a technique of self-indoctrination: "Doublethink . . . is a vast system of mental cheating" (George Orwell).

Equivocate to use ambiguous or unclear expressions, usually to avoid commitment or in order to mislead; prevaricate or hedge.

I assume, since I'm the author of this post, that your comment was directed primarily at me. Greater Greater Washington has many contributors. While many of us have similar opinions, we don't share a hive mind, so if different posts disagree with each other, it's not because we can't make up our minds. It's because we're individuals.

David A. asked me to write a post about the derailment because I have some understanding of the safety systems Metro has in place, although I am in no way an expert. He felt that the media was sensationalizing the story and was ignoring the fact that the derailment was part of the safety system and not the problem itself.

There is no doublethink in this post. In fact, there's little opinion whatsoever. The post starts out by introducing readers to the situation (there was a derailment), bringing known facts to the table (3 minor injuries), and describing what was known about the incident (it happened at the north end of the pocket).

Since a piece of technology was used that most are unfamilar with, the post then goes on to give detail about the setting (describe the pocket), references other related systems (signals, ATC), gives a detailed description of the piece of technology in question (the derailer), and talks briefly about the purpose and intent of the device (absolutely will stop a train).

This discussion was followed by one example of a derailer failing (in Newark Bay, NJ) and then a few concluding remarks summing up the post and reminding readers that we don't know the cause yet.

None of that is doublethink. None of that is equivocating. The post was intended to be as clear an expanation as possible of the incident, the technology, and the circumstances. I did not mislead, prevaricate, or hedge on anything, and certainly did not do so in an attempt to indoctrinate myself.

I certainly am not, and I don't think any of the other contibutors are blind defenders of Metro. This blog has been an outspoken critic of and an outspoken advocate for Metro. In this case, it was important to give our readers details. It is far too early to lay blame. What is most important, however, is that Metro's safety systems worked. A few minor injuries and some delays are much, much better than another collision.

It would be better if this had not happened, and Metro will hold someone to account for this. But the system still remains far safer than other modes of travel, it remains one of the driving forces of our regional economy, and it remains one of our greatest assets.

There is certainly room for improvement though.

by Matt Johnson on Feb 16, 2010 10:15 am

I am concerned that the original post did seem to make this latest accident out to be a success story. In fact, I see it as the latest in a string of incidents where Metro employees failed miserably. In this case, the train was directed into the pocket track and the operator ran a red signal. These are apparently failures of significant degree, and again, just the latest examples of malfeasance on the front line at Metro. Heads need to roll, setting an example of zero tolerance for this type of stuff!!!

by KevinM on Feb 17, 2010 6:59 am

KevinM,

That as my first inclination as well, but then I realized that every single news report on the incident didn't seem to offer a coherent explanation of exactly what happened. This post is the only thing that did so.

Draw your own conclusions from that, but having the correct information is a big bonus.

by Alex B. on Feb 17, 2010 8:07 am

I was on an 8-car, Glenmont-bound train Friday that arrived at Farragut North within a minute or two of 10:13 a.m., when the derailment occurred. Any way to know how close I came to disaster?

by David S. on Feb 17, 2010 6:27 pm