Derailment causing disruption at Sheffield 09-10-2018

[MarkyT]

The signalling on departing Lovers Walk Depot has been altered to prevent a train approaching the said shunt signal unless it is showing a proceed first, meaning that the trap points will always be set first before a train can approach form the previous shunt signal. So unless we have a double SPAD or a runaway we shouldn’t have any more.

Back to Sheffield and if they are still using the same numbering at York ROC that Sheffield used prior to its migration and from the picture evidence. Then the train should of been waiting at shunt signal 92, it then moved over 4048 trap points set against it.

The resulted in track 171 track circuit interrupter operating (TCI), that would lock all point that go through that track circuit into their last called position which were 4055A2 normal , 4055A1 normal , 4055B normal, 4048 normal, 4049B and 4049A both reverse, when the track circuit flooded, (this assumes that TCI only effects one track which most only do).

Looking at that picture points 4049 A+B that come off line Down Main/A into platforms one and two were now locked reverse because of the TCI activation. You can’t signal northbound into platforms one and two because of the flooded track circuit, you also can’t signal soothbound into platform one and use the whole platform because of the flooded track in the signal overlap, but they could of been able to signal trains up to signal 116 depending on the signal overlaps. and can’t signal southbound into platform two because points 4049 A+B are locked reverse because of the flooded track.

If they did a release of signalling controls (which is a once only event which requires no train movements within the interlocking area) they could false clear tack circuit 171 to allow points 4049 A+B to be moved into the normal position. Once this is done then they must restore the equipment back to its correct state which re flood track circuit 171. but that would give you platform two back into use from the north and also from the south if they were allowing trains to pass the offending units under normal signalling.

Platform one from the north might require dropping the track circuits in platform on purpose to use the call on even though there would be no train in there assuming that points 4049 A+B are not required in the reverse.

Not sure if any signalling cables were actually damaged or not as reading this thread it only seems they might of been but the activation of the TCI would of caused most if not all of the chaos.

A great explanation! Interrupters were specifically developed so that if a derailment completely leaves the rails with no axles remaining on the track, and the wreckage potentially lying foul of adjacent tracks, the TC through the junction remains occupied to prevent further movements in the vicinity.

 

[Sunset route]

A great explanation! Interrupters were specifically developed so that if a derailment completely leaves the rails with no axles remaining on the track, and the wreckage potentially lying foul of adjacent tracks, the TC through the junction remains occupied to prevent further movements in the vicinity.

Of course we now have buffer stop interrupters that are desisigned to have the same effect as in flooding the relevant track circuits if the buffers are struck above a certain force. Not sure when they come about but we have 7 on our patch now since 2009 as various places that have had minor and not so minor signalling alterations.

 

[MarkyT]

Of course we now have buffer stop interrupters that are desisigned to have the same effect as in flooding the relevant track circuits if the buffers are struck above a certain force. Not sure when they come about but we have 7 on our patch now since 2009 as various places that have had minor and not so minor signalling alterations.

Short buffer stop spurs have been preferred over simple traps in new layouts for decades and can sometimes be implemented fairly easily even in small scale routine junction renewals, but it's a slow process to modernise more complex cases, as the spurs can't always be accommodated easily in older layouts, and there can be assets in the way like washer plant rooms, other buildings, electrification plant and structures. So traps may have to be tolerated until more comprehensive redesign of a junction, including safer siding throw offs, often as part of a subsequent major resignalling where both track and signal assets are renewed together allowing easier reconfiguration. Meanwhile, simple pragmatic measures to manage risk can be implemented, as at Brighton. I guess it makes using the line as a depot headshunt more difficult if you need a route set forward into a platform every time, but at least there are alternative routes available for other movements through the extensive parallelism of the throat.

 

[Chris M]

Are there any cranes or breakdown trains left anywhere on the network now or are such incidents yet another aspect of rail operation which is outsourced to private contractors?

Speaking to the people re-railing the HST power car in Paddington last August, cranes aren't the tool of choice unless the vehicle involved has fallen over or has travelled significantly far away from a track on which it can be put back on to. For most incidents, jacking is the preferred method of rerailing - even more so when there is OHLE.

My impression is that Network Rail did a piece of work in the aftermath of the incident at Paddington and determined that there were no other locations where OHLE had been installed directly in front of catch or trap points.

Do the trap points at Castle Cary still point directly at the legs of the footbridge?

 

[MarkyT]

Do the trap points at Castle Cary still point directly at the legs of the footbridge?

I believe they do, but it is a very infrequently used siding, not a busy exit from a depot or goods line, so the number of signal approaches will be very small indeed.