A wrong-side failure describes a failure condition in a piece of railway signalling equipment that results in an unsafe state. A typical example would be a signal showing a 'proceed' aspect (e.g. green) when it should be showing a 'stop' or 'danger' aspect, resulting in a "false clear". (The converse is a right-side failure, where even with any reduction the resulting state is safe overall.)
Consider a relay that has to energize to show a green light.
If a wire breaks, or the battery is drained, then the relay will de-energize and the signal will show a red light, which is fail-safe.
If a stray wire from another circuit touches the wire connected to that same relay, then that would be a wrong side failure, which is potentially dangerous. This stray wire can be guarded against by ensuring that the insulation on the relay wire is of good quality, and that all terminals are locked away.
In addition, the relay may be double-switched, also known as double-cut, that is to say that it only energizes if a positive circuit and a negative circuit are both complete. That would then require two stray wires to cause a wrong-side failure, which is much less likely than a single stray wire.
Accidentsedit
While accidents from the problem are rare, they do occur:
1915 – Rockledge, Tennessee – Relocation of a Western Union telegraph line from old alignment to new alignment causes a false clear signal indication when the Western Union wire comes in contact with the signal wire for the automatic block signal at the south end of the siding at Rockledge. A southbound freight train departed Rockledge on the false clear indication and collided with a northbound passenger train that had entered the block at Tantallon on a proper clear indication two minutes before the freight train departed Rockledge. A contributing factor was that the tower operator at Rockledge only controlled the signals, the track switches being operated by the train crews themselves.
1927 – Marrar (NSW, Australia) – lightning damage meant that the single line train tablet system incorrectly released two tablets simultaneously putting two trains on a collision course; fortunately they saw each other and were able to stop in time.[1]
1976 – Glenbrook, New South Wales (Australia) Automatic signal in rear of a stationary EMU at "caution" when it should have been at "danger". Following goods train enters occupied signal section and collides with EMU; 1 passenger killed. Cause attributable to deteriorated wiring which allowed a false feed.
1979 – Invergowrie rail crash (Scotland) – signal was at "wrong" (i.e. indistinct indication) yet taken by driver to be a 'proceed' signal.
1982 – Valley Heights train collision (NSW, Australia) – electrician wrongly replace out clear glass lenses with coloured glass causing false colour with reflected sunlight.[2]
1988 – Clapham Junction rail crash (London) – single stray wire causes false green signal and collision killing 35.
1990 – Cowan rail disaster (NSW, Australia), which occurred when sand on the rails insulated the wheels from the rails, causing a failure to shunt that allowed a trailing block signal to improperly display a clear aspect, resulting in a rear-end collision.
2005 – Deelfontein (South Africa) – solder splatter bridges a relay contact. Most testing is done with the relays unplugged which would not detect the splatter, while the solder splatter is likely to lead to a difficult to trace phantom problem.
2009 – On March 26, two trains collided near Arévalo, Spain while engineers were testing a new signalling system. Lack of safeguards and testing on an active line led to the collision of two freight trains. One of the train drivers died.[3]
2009 – Ft Totten crashWashington DC Metro (WMATA). An inbound Red Line train stopped short of Ft. Totten station; the following train failed to stop and impacted at about 42 mph (68 km/h). Nine dead, 80 injured. Preliminary NTSB reports were that the AC track circuit transmitter was breaking into parasitic oscillation, and that coupled across the rack cabinet to the receiver.
2020 – On the Italian high speed rail network, maintenance workers during the night left a faulty point to the reverse position, but disconnected its network connection and its link to the safety signalling system (ETCS L2); the first morning high speed train received a green signal to proceed at full speed and hit the point at 181 mph (291 km/h), resulting in the Livraga derailment which killed 2 and injured 31.
False alarmsedit
Railway authorities usually give the drivers and signalmen the benefit of the doubt and investigate whether a wrong-side failure is the cause of an accident. This occurred with the Hinton train collision, but investigations soon showed that a wrong-side failure was not the cause.
^"Railway Safety". The Sydney Morning Herald. No. 28073. New South Wales, Australia. 27 December 1927. p. 7. Retrieved 4 January 2018 – via National Library of Australia.
^Doctornickau (9 November 2008). "StateRail - Early 1980s Valley Heights Train crash". YouTube. Archived from the original on 2021-12-12. Retrieved 4 January 2018.
^"Informe Final Sobre el Accidente Ferroviario No 0018/2010 Ocurrido el Día 26.03.2010 en las Proximidades de la Estación de Arévalo (Ávila)" [Final Report on Railway Accident No. 0018/2010 occurring on 26 March 2010 near Arévalo Station (Ávila)] (PDF). Ministerio de Fomento (in Spanish). Retrieved 4 January 2018.
^Lopez, Robert J. & Connell, Rich (21 January 2010). "Investigators: Light was red in 2008 Chatsworth train crash, despite what witnesses said". Los Angeles Times. Retrieved 4 January 2018.
^Witnesses: Doomed train had green light - Wikinews, October 7, 2008.
External linksedit
False proceed
Notifiable incidents
January 01, 1970
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This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Wrong side failure news newspapers books scholar JSTOR July 2010 Learn how and when to remove this message A wrong side failure describes a failure condition in a piece of railway signalling equipment that results in an unsafe state A typical example would be a signal showing a proceed aspect e g green when it should be showing a stop or danger aspect resulting in a false clear The converse is a right side failure where even with any reduction the resulting state is safe overall Contents 1 Example of how a wrong side failure may occur 2 Accidents 3 False alarms 4 Wrong side failures to be reported 5 See also 6 References 7 External linksExample of how a wrong side failure may occur editThis section possibly contains original research Please improve it by verifying the claims made and adding inline citations Statements consisting only of original research should be removed June 2023 Learn how and when to remove this message Consider a relay that has to energize to show a green light If a wire breaks or the battery is drained then the relay will de energize and the signal will show a red light which is fail safe If a stray wire from another circuit touches the wire connected to that same relay then that would be a wrong side failure which is potentially dangerous This stray wire can be guarded against by ensuring that the insulation on the relay wire is of good quality and that all terminals are locked away In addition the relay may be double switched also known as double cut that is to say that it only energizes if a positive circuit and a negative circuit are both complete That would then require two stray wires to cause a wrong side failure which is much less likely than a single stray wire Accidents editWhile accidents from the problem are rare they do occur 1876 Abbots Ripton rail disaster England signals frozen by blizzard in clear position signal arm hidden in a slot in the post 1915 Rockledge Tennessee Relocation of a Western Union telegraph line from old alignment to new alignment causes a false clear signal indication when the Western Union wire comes in contact with the signal wire for the automatic block signal at the south end of the siding at Rockledge A southbound freight train departed Rockledge on the false clear indication and collided with a northbound passenger train that had entered the block at Tantallon on a proper clear indication two minutes before the freight train departed Rockledge A contributing factor was that the tower operator at Rockledge only controlled the signals the track switches being operated by the train crews themselves 1927 Marrar NSW Australia lightning damage meant that the single line train tablet system incorrectly released two tablets simultaneously putting two trains on a collision course fortunately they saw each other and were able to stop in time 1 1938 Charing Cross Northern line tube crash London signal linesman rewires a faulty signal incorrectly so that it shows green too soon two Underground trains collide as a result injuring twelve Also Charing Cross District line tube crash signal linesman makes wiring error in cabin two Underground trains collide killing six 1953 Sydenham Rail Disaster NSW Australia five killed 1976 Glenbrook New South Wales Australia Automatic signal in rear of a stationary EMU at caution when it should have been at danger Following goods train enters occupied signal section and collides with EMU 1 passenger killed Cause attributable to deteriorated wiring which allowed a false feed 1979 Invergowrie rail crash Scotland signal was at wrong i e indistinct indication yet taken by driver to be a proceed signal 1982 Valley Heights train collision NSW Australia electrician wrongly replace out clear glass lenses with coloured glass causing false colour with reflected sunlight 2 1988 Clapham Junction rail crash London single stray wire causes false green signal and collision killing 35 1990 Cowan rail disaster NSW Australia which occurred when sand on the rails insulated the wheels from the rails causing a failure to shunt that allowed a trailing block signal to improperly display a clear aspect resulting in a rear end collision 2005 Deelfontein South Africa solder splatter bridges a relay contact Most testing is done with the relays unplugged which would not detect the splatter while the solder splatter is likely to lead to a difficult to trace phantom problem 2009 On March 26 two trains collided near Arevalo Spain while engineers were testing a new signalling system Lack of safeguards and testing on an active line led to the collision of two freight trains One of the train drivers died 3 2009 Ft Totten crash Washington DC Metro WMATA An inbound Red Line train stopped short of Ft Totten station the following train failed to stop and impacted at about 42 mph 68 km h Nine dead 80 injured Preliminary NTSB reports were that the AC track circuit transmitter was breaking into parasitic oscillation and that coupled across the rack cabinet to the receiver 2020 On the Italian high speed rail network maintenance workers during the night left a faulty point to the reverse position but disconnected its network connection and its link to the safety signalling system ETCS L2 the first morning high speed train received a green signal to proceed at full speed and hit the point at 181 mph 291 km h resulting in the Livraga derailment which killed 2 and injured 31 False alarms editRailway authorities usually give the drivers and signalmen the benefit of the doubt and investigate whether a wrong side failure is the cause of an accident This occurred with the Hinton train collision but investigations soon showed that a wrong side failure was not the cause The 2008 Chatsworth train collision was determined to be human error not wrong side failure as a few initially said 4 Wrong side failures to be reported editIn the United States there is a rule that wrong side failures are to be reported to the Federal Railroad Administration 5 See also editLists of rail accidentsReferences edit Railway Safety The Sydney Morning Herald No 28073 New South Wales Australia 27 December 1927 p 7 Retrieved 4 January 2018 via National Library of Australia Doctornickau 9 November 2008 StateRail Early 1980s Valley Heights Train crash YouTube Archived from the original on 2021 12 12 Retrieved 4 January 2018 Informe Final Sobre el Accidente Ferroviario No 0018 2010 Ocurrido el Dia 26 03 2010 en las Proximidades de la Estacion de Arevalo Avila Final Report on Railway Accident No 0018 2010 occurring on 26 March 2010 near Arevalo Station Avila PDF Ministerio de Fomento in Spanish Retrieved 4 January 2018 Lopez Robert J amp Connell Rich 21 January 2010 Investigators Light was red in 2008 Chatsworth train crash despite what witnesses said Los Angeles Times Retrieved 4 January 2018 Witnesses Doomed train had green light Wikinews October 7 2008 External links editFalse proceed Notifiable incidents Retrieved from https en wikipedia org w index php title Wrong side failure amp oldid 1192754923, wikipedia, wiki, book, books, library,
