Bi-Directional Signalling

[D Foster]

What is the correct name for "part time" / "emergency" Bi-Directional signalling please?

Thanks

 

[pdeaves]

What is the correct name for "part time" / "emergency" Bi-Directional signalling please?

I presume that you are referring to simplified bi-directional signalling, or SIMBIDS for short.

 

[MarkyT]

I presume that you are referring to simplified bi-directional signalling, or SIMBIDS for short.

SIMBIDS: A redundant term, originally used in the 1980s and 90s for lower capacity reverse direction signalling retrofitted to relay equipped areas where full AWS facilities were not provided as an economy measure, saving a lot of complexity associated with suppression magnets, cables and wiring. Also the term was used colloquially on the Southern Region where reduced capacity reverse direction signalling was provided WITH full AWS provision for example on the Brighton line. Today the term does not appear at all in any official operational or technical publications, and the non provision of full AWS is not allowed on any new schemes, being removed for example in GWML resignalling where 'real' SIMBIDS had been installed in certain sections west of Swindon.

 

[Jamesb1974]

Deleted

 

[MarkyT]

What is the correct name for "part time" / "emergency" Bi-Directional signalling please?

Thanks

There is no specific term for this, it is just regular TCB, however any particular restrictions or procedures would be covered by specific general or local instructions in the appropriate sectional appendix.

For example on the Western -

REVERSIBLY SIGNALLED LINES BETWEEN FOXHALL JUNCTION AND THINGLEY JUNCTION AND BETWEEN WOOTTON BASSETT JUNCTION AND CHIPPING SODBURY.

Reversible working may be introduced on sections of line between the locations shown above at any time for traffic purposes or during engineering work, train failure, infrastructure failure or damage or obstruction of the line. Drivers and others concerned must be prepared for reversible working to be introduced at any time without advance warning being provided.

When used for traffic purposes, trains concerned will normally be worked in the same direction. For example, during periods of service disruption, a slower train could be signalled reversibly to allow a faster train to overtake in the normal direction on the usual line.

If it is necessary for both lines to be worked in the wrong direction simultaneously, i.e. down trains signalled on the up line and up trains signalled on the down line, all drivers affected will be advised of the circumstances prior to entering the section concerned.

REVERSIBLY SIGNALLED ROUTES BETWEEN THINGLEY JUNCTION AND NORTH SOMERSET JUNCTION

Conditions of use. Reversible working of trains can only be introduced on sections of this route when one line is not
available because of :

• engineering work
• train failure
• infrastructure failure or damage
• obstruction of the line.

AWS arrangements. In the reverse direction, AWS is provided only for temporary and emergency speed restrictions.

AWS inductors for normal direction signals are not suppressed when reverse direction movements are signalled and drivers must cancel all such warnings. Reminder signs as shown in rule book handbook RS/521, section 5.16 are provided at the start and finish of each reversible section.

Signal post telephones. Many reverse direction signals in these sections do not have separate signal post telephones. Where this is so, traincrew must use the telephone at the parallel signal on the other line and must specially ensure that the signaller understands which signal their train is detained at.

Western Route GI - Dated: 05/03/16

Note the second section between Thingley and North Somerset Jcns is one of the original SIMBIDS sections I was referring to, and the entry has reminded me of another economy measure used at the time - not providing separate signal post telephones for some of the wrong direction signals.

 

[Ploughman]

Another area were SIMBIDS was used is the ECML between Newcastle and Northallerton.
Crossovers and signalling all upgraded.

 

[D Foster]

Thanks for the speedy replies
Apologies for not getting back before - been busy.

I thought that this provision was more common???

One item I have noticed is a strange X sign (red on white I think) in the right hand cess which would display for traffic running "wrong direction"? I seem to recall being told that it was something to do with partial "bi-di" working - possibly in connection with where AWS was for right direction??? Not sure if this makes any sense at all... The one I've seen was in the Preston Brook area.

Thanks

 

[Tomnick]

White cross on a square blue background? It's a cancelling indicator, if so - indicates to the driver that the AWS warning that's just been received is applicable to movements in the other direction only, and can be disregarded.

 

[MarkyT]

Thanks for the speedy replies
Apologies for not getting back before - been busy.

I thought that this provision was more common???

One item I have noticed is a strange X sign (red on white I think) in the right hand cess which would display for traffic running "wrong direction"? I seem to recall being told that it was something to do with partial "bi-di" working - possibly in connection with where AWS was for right direction??? Not sure if this makes any sense at all... The one I've seen was in the Preston Brook area.

Thanks

Try the Master Rule Book,

Signals,
handsignals,
indicators and signs
Handbook
RS/521 Issue 3
December 2015

Section 5.16, AWS gap indicators, (page 1367 of the pdf below)

http://www.rssb.co.uk/rgs/rulebooks/GERM8000-master-module Iss 2.pdf

I think it's the lower diamond shaped ones you are referring to. These were provided for the original SIMBIDS installations, and some of these remain in place with the cut price signalling of the time covered by instructions in the sectional appendix like the Western Route one I quoted earlier. These signs indicate a lack of AWS in the reverse direction, and also that there could be (will be) non-suppressed spurious warnings encountered at the magnets for the normal direction signals that must be cancelled and ignored. Normally if there's a meaningless AWS horn on a single line, say on a rural branch with a fixed distant where the magnet isn't suppressed, then an individual cancelling indicator sign (section 5.15) is provided for each such magnet where a signal would be in the wrong direction, i.e 200 yards or so beyond the magnet. Once you pass one of the red cross diamond signs however, ALL AWS indications must be ignored and cancelled as necessary until you get to the end of section sign. The round sign is different, meaning there is no AWS equipment at all so no need to cancel any spurious warnings.

 

[D Foster]

Thanks again!!!

 

[Ploughman]

Same document section 4.2 shows a Black Cross on a white background for wrong direction working.
This also incorporates a speed limit.
These signs normaly used for wrong direction working through Level Crossings, mainly AHB as found on the Hull - Bridlington line for example.