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Metro's Not So Fail-Safe System

* Live Webcast, NOW: House Hearing on Metro Crash *

The term entered the common language during the Cold War when Eugene Burdick wrote an arms-race thriller called "Fail-Safe." The scenario seems dated now: To the stunned surprise of controllers, U.S. nuclear bombers move past the point at which they're supposed to stop. But it's still a ripper, because of the well-known principle the 1962 novel illustrated: If something can go wrong, eventually it will. Nothing built by humans is "Fail-Safe."

Metro's operations control center isn't as impressive as the Strategic Air Command's headquarters, with its towering maps and flashing lights, but it's basically the same function: Redundant protections are supposed to make the train system fail-safe. But ultimately, humans are making sure the equipment is going where it's supposed to go.

On June 22, a fail-safe system failed to prevent the fatal crash of two Metrorail trains on Washington's Red Line. And the National Transportation Safety Board told us on Monday that we have no system in place to ensure that this won't happen again.

What does this mean to riders?

-- Thank your driver. If the electronics fail, the last line if defense is the ability of the train operator to see ahead and stop the train. Still, this last line of defense failed to prevent the June 22 crash and we don't know why. Is there something unusual -- like limited sight lines -- in that stretch of track between Takoma and Fort Totten?
-- Our trains are likely to be under the control of the operators for a long time. Metro doesn't have a system in place to do what the NTSB urgently recommends: Automatically catch a problem that the train controllers can't see and prevent a crash. Metro says that such a system has to be made and delivered to Metro.
-- Trains are likely to be stopping at the front of the platforms for a long time. If trains are under manual control, there's always a chance that an operator would forget how long the train is and open the doors before all the cars are at the platform. The easiest solution is to tell all operators to stop at the front of the platform, so a train of any length will fit safely.
-- The current delays on the Red Line are not related to the manual control of the trains. We haven't heard anything so far from the NTSB or Metro that suggests the Red Line delays will spread to other lines. But neither is it any clearer how long the Red Line delays will continue. [Update: The Takoma Station will be open till midnight tonight and Wednesday night. Then the NTSB will resume its crash investigation at 10 p.m. Thursday, again closing Takoma. Whenever Takoma is closed, free shuttle buses will take passengers between Silver Spring, Takoma and Fort Totten stations.]
-- Metrorail is statistically a very safe way to travel. But the same train control system that is supposed to prevent crashes when the trains are under automatic control is supposed to prevent them when they're under manual control. To me, that's what's especially urgent about the NTSB recommendation to Metro that it find a backup alert system.


By Robert Thomson  |  July 14, 2009; 1:15 PM ET
Categories:  Metro , Safety  | Tags: Dr. Gridlock, Metrorail delays, Red Line crash  
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Comments

All right, I'll be the word nerd here. Although it does not substantially alter your point, "fail-safe" is used incorrectly in this post and frequently in the Post and elsewhere.

"Fail-safe" does not mean it won't fail. That's "failure-proof." "Fail-safe" means that if it does fail, it goes into a state that will cause no harm. In this example, a "fail-safe" Metro track sensor is one that, if it fails, won't let the train move ahead even if the track is clear. That obviously wasn't the case on the Red Line -- it was nether failure-proof (it failed) nor fail-safe (when it failed, it allowed a dangerous situation.)

Aah. Thank you.

Posted by: airsix | July 14, 2009 2:12 PM | Report abuse

I was amused by this from today's story on the NTSB recommendations:

** In a statement yesterday, Metro said there are currently no systems available commercially that could provide the transit agency with the kind of alerts the safety board has recommended. "Such a system must be invented," the statement said. **

Yeah, because it's really hard to use existing sensing & signaling technology to detect the presence of something as small as a freakin' TRAIN, you know?

Posted by: bobsewell | July 14, 2009 2:49 PM | Report abuse

I second airsix's comment and would also point the post author to http://en.wikipedia.org/wiki/Fail-safe

Posted by: heartprivacy | July 14, 2009 3:10 PM | Report abuse

They have to "invent" a system to prevent two trains from entering the same signaling block, a system that New York and other subway systems have had in place since the early 1900s?

BTW, lack of funding was NOT a factor in this accident -- the lack of redundancy in this not-fail-safe train control system system made it unsafe BY DESIGN.

Posted by: stuckman | July 14, 2009 9:43 PM | Report abuse

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