Comments on: Metro trains crash: time for automated equipment http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/ Putting Transit On The Fast Trackā„¢ Mon, 08 Feb 2010 06:42:38 +0000 hourly 1 http://wordpress.com/ By: anonymouse http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-260 anonymouse Tue, 30 Jun 2009 05:15:05 +0000 http://switchingmodes.com/?p=1045#comment-260 Let me put it as simply and clearly as I can: the root cause is not the architecture of the signal system or how "advanced" it is or is not. Systems of the type used in Washington can be made to be safe, but safety is not something you buy in a box. Safety takes constant vigilance, competence, and a strong safety culture. This incident once again shows that WMATA does not have some or all of the above. The root cause of the accident is the action of a signal engineer who failed to understand the implications of his design, or of a signal maintainer who failed to understand the consequences of his actions. And ultimately, it is the failure of the system as a whole to provide a check on their actions, to ensure that when people inevitably make mistakes, they are caught and fixed before they become dangerous. As for "advanced" systems, I think they can provide benefits, but also have their cost. And the main cost is that implied by the very term "advanced": complexity. Complexity makes them harder to design, and harder to verify that they're acting as they're supposed to. And if they're not tested fully, then they may fail, and when they do, it will be in some particularly unusual case where conditions are already far from normal, and that makes for a very dangerous situation. Let me put it as simply and clearly as I can: the root cause is not the architecture of the signal system or how “advanced” it is or is not. Systems of the type used in Washington can be made to be safe, but safety is not something you buy in a box. Safety takes constant vigilance, competence, and a strong safety culture. This incident once again shows that WMATA does not have some or all of the above. The root cause of the accident is the action of a signal engineer who failed to understand the implications of his design, or of a signal maintainer who failed to understand the consequences of his actions. And ultimately, it is the failure of the system as a whole to provide a check on their actions, to ensure that when people inevitably make mistakes, they are caught and fixed before they become dangerous.

As for “advanced” systems, I think they can provide benefits, but also have their cost. And the main cost is that implied by the very term “advanced”: complexity. Complexity makes them harder to design, and harder to verify that they’re acting as they’re supposed to. And if they’re not tested fully, then they may fail, and when they do, it will be in some particularly unusual case where conditions are already far from normal, and that makes for a very dangerous situation.

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By: Jersey Mike http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-258 Jersey Mike Mon, 29 Jun 2009 16:56:37 +0000 http://switchingmodes.com/?p=1045#comment-258 Advanced automation technologies usually mean various types of CBTC (wireless) train control and these are far less reliable and completely untested when it comes to their relative safety. The #1 driver behind technologies like CBTC is cost reduction. They cost less to maintain and less to train operators. In return they are buggy, allow for slower speeds and are often unreliable. Philadelphia replaced a traditional block signal system on its sub-surface trolley line in the interest of "safety" and it double trio times from 20 to 40 minutes. How many people will die in their cars because this "upgrade" has made the system half as fast? Advanced automation technologies usually mean various types of CBTC (wireless) train control and these are far less reliable and completely untested when it comes to their relative safety. The #1 driver behind technologies like CBTC is cost reduction. They cost less to maintain and less to train operators. In return they are buggy, allow for slower speeds and are often unreliable. Philadelphia replaced a traditional block signal system on its sub-surface trolley line in the interest of “safety” and it double trio times from 20 to 40 minutes. How many people will die in their cars because this “upgrade” has made the system half as fast?

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By: Jersey Mike http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-257 Jersey Mike Mon, 29 Jun 2009 12:20:56 +0000 http://switchingmodes.com/?p=1045#comment-257 It wasn't a problem with the method of signaling, but instead a Wrong Side Failure that gave a false proceed. It wasn’t a problem with the method of signaling, but instead a Wrong Side Failure that gave a false proceed.

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By: Adirondacker http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-256 Adirondacker Mon, 29 Jun 2009 08:26:21 +0000 http://switchingmodes.com/?p=1045#comment-256 If you are defining positive train control as "stop the train if it moves through a stop signal" - which is the signal the train in DC should have had - then that's been around for more than 100 years. You don't need computers to enforce it. Don't even need electricity to enforce it. http://www.nycsubway.org/tech/signals/stops.html If you are defining positive train control as “stop the train if it moves through a stop signal” – which is the signal the train in DC should have had – then that’s been around for more than 100 years. You don’t need computers to enforce it. Don’t even need electricity to enforce it.

http://www.nycsubway.org/tech/signals/stops.html

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By: Switching Modes http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-255 Switching Modes Mon, 29 Jun 2009 04:03:02 +0000 http://switchingmodes.com/?p=1045#comment-255 anonymouse, I agree with your statement that newer systems should take into account the short comings of systems that preceded them, but I disagree that newer automated systems would neither "help or hurt in this case." Please read my response to Jersey Mike's article... anonymouse,
I agree with your statement that newer systems should take into account the short comings of systems that preceded them, but I disagree that newer automated systems would neither “help or hurt in this case.” Please read my response to Jersey Mike’s article…

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By: Switching Modes http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-254 Switching Modes Mon, 29 Jun 2009 03:56:54 +0000 http://switchingmodes.com/?p=1045#comment-254 Jersey Mike, Perhaps I should have added the name 'advanced' before automated equipment. The point is that our train control technology is out of date. I disagree with your statement that automated equipment makes trains less safe; to the best of my knowledge there is not advanced automated train control system in the world that has had a fatality. NOTE: I wrote the article to be simple, so I didn't go into different technologies. When I speak of advanced automated systems, I mean automated system which incorporate positive train control. In short, these systems put the control of the train in the hand of an on board computer, rather than a central control unit. The two primary advantages are that they are safer and less costly to operate. Additionally, such systems can allow trains to run at lower headway times. Sorry you might have misinterpreted the article. Jersey Mike,
Perhaps I should have added the name ‘advanced’ before automated equipment. The point is that our train control technology is out of date. I disagree with your statement that automated equipment makes trains less safe; to the best of my knowledge there is not advanced automated train control system in the world that has had a fatality.

NOTE: I wrote the article to be simple, so I didn’t go into different technologies. When I speak of advanced automated systems, I mean automated system which incorporate positive train control. In short, these systems put the control of the train in the hand of an on board computer, rather than a central control unit. The two primary advantages are that they are safer and less costly to operate. Additionally, such systems can allow trains to run at lower headway times.

Sorry you might have misinterpreted the article.

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By: anonymouse http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-253 anonymouse Fri, 26 Jun 2009 23:33:51 +0000 http://switchingmodes.com/?p=1045#comment-253 In this case, the train was almost certainly running in full automatic mode, and the cause of the crash was a track circuit that failed to detect the train ahead. I don't think that automation actually had anything to do with this: if the train operator were running the train in manual mode, she would still have seen a cab signal indication allowing full speed, and the train would have been going just as fast. With conventional trackside signals, the train would have gotten a green signal. I don't think automation would help or hurt in this case in particular, but perhaps we need to be much more cautious of newer signalling technology whose designers may have forgotten the lessons learned in prior decades, lessons paid for with people's lives. In this case, the train was almost certainly running in full automatic mode, and the cause of the crash was a track circuit that failed to detect the train ahead. I don’t think that automation actually had anything to do with this: if the train operator were running the train in manual mode, she would still have seen a cab signal indication allowing full speed, and the train would have been going just as fast. With conventional trackside signals, the train would have gotten a green signal. I don’t think automation would help or hurt in this case in particular, but perhaps we need to be much more cautious of newer signalling technology whose designers may have forgotten the lessons learned in prior decades, lessons paid for with people’s lives.

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By: Jersey Mike http://switchingmodes.com/2009/06/22/metro-trains-crash-time-for-automated-equipment/#comment-249 Jersey Mike Thu, 25 Jun 2009 12:48:29 +0000 http://switchingmodes.com/?p=1045#comment-249 For someone with a transit blog you sure don't seem to know a lot about transit systems work. The DC Metro uses an automated system. There was most likely a track circuit detection failure in the signaling system. There was a similar incident in 2005 where the on board driver hit the emergency brake and got his train stopped when the automated system was about the drive the train into the one in front. ZPTO makes trains less safe, not more. It might work in an airport, but not a real transit system. For someone with a transit blog you sure don’t seem to know a lot about transit systems work. The DC Metro uses an automated system. There was most likely a track circuit detection failure in the signaling system. There was a similar incident in 2005 where the on board driver hit the emergency brake and got his train stopped when the automated system was about the drive the train into the one in front.

ZPTO makes trains less safe, not more. It might work in an airport, but not a real transit system.

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