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Railway Gazette: Signal failure suspected in Wenzhou crash

CHINA: `Design flaws' in the signalling on the Ningbo - Wenzhou high speed line led to the fatal rear-end collision near Wenzhou on July 22, according to the recently-appointed head of the Shanghai Railway Bureau An Lusheng. The accident is now reported to have killed 39 people and injured 192.

Appearing on July 28 before the independent investigation panel established by the State Council, An said that `having been struck by lightning, the signal system at Wenzhou South station failed to turn a green light to red'. On the same day, the Beijing National Railway Research & Design Institute of Signal & Communication issued an apology for the accident.

...Although An's statement indicated a wrong-side failure, unofficial reports quoting railway insiders suggest that the signalling may have failed safe following the lightning strike, and that operations had been resumed using radio dispatching. There have also been suggestions that train D3115 between Hangzhou and Fuzhou was halted by activation of an emergency passenger alarm 23 min before the collision, but this information had not been relayed to the driver of the following Beijing - Fuzhou train D301.

The information in the media is too contradictory to say much more than what I said earlier. Still, indications are that there were failures at multiple levels: failure of the automatic train protection system, failure in the design of the automatic train protection system, failure on the part of the train dispatchers at the control centre (who oversee train operation like air traffic controllers), and failure of communication.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Aug 5th, 2011 at 02:58:31 PM EST
[ Parent ]
I don't understand the signal bit?  Do they really use light based signalling on these lines, surely at such speeds it must all be in cab?
by njh on Sat Aug 6th, 2011 at 11:10:08 PM EST
[ Parent ]
Opened on September 28 2009, the Yongtaiwen Railway between Ningbo and Wenzhou South is equipped with lineside signals overlaid with CTCS-2 to provide automatic train protection. This has a similar functionality to ETCS Level 1, using balises to provide intermittent updates to the on-train equipment. The line is designed for mixed traffic operation with a maximum speed of 250 km/h.

Cab signalling can be required for speeds as low as 140 km/h, showing the state of the lineside signal in advance, thus co-existence with actual lineside signals is common. The combination is actually a good idea: the lineside signals can function as a fallback level (also see the experience with the Madrid-Barcelona line). Also, the reported claim is about a signal at a station, where trains that stop go slow.

At any rate, in an ETCS L1 equivalent system, if the lineside signal shows green instead of red, the cab signal will show the same; and even if there is no lineside signal, until the advent of moving block signalling, signal states shown by cab signalling will be associated with fixed locations.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Aug 7th, 2011 at 03:28:40 AM EST
[ Parent ]
Ok, so how does lightning affect the in cab system so that it shows all clear?  Surely it is all designed to fail safe?
by njh on Sun Aug 7th, 2011 at 10:06:29 PM EST
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To say it another way, the in-cab system is not a track-independent signalling system, but a signal repeater: the state of the signal induces the state of the information transmitted by the balise, which is received by the locomotive. It has no way to tell that the signal information is wrong.

OTOH signals themselves are supposed to fail safe (show red if there is any disturbance), so if the ministry told the truth about the signal failure, it is a fundamental grave error.

But either way, again, what happened at the train control centre? They should have noticed that the second train passed the signal, even on radio communication. There is the human attitude problem that they assume automatic systems to work fine and grow lax, but even so, with an emergency situation on-going for 23 minutes, they should have been on alert.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Aug 8th, 2011 at 06:42:52 AM EST
[ Parent ]

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