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North East Scotland

Features

Methods of Working

Three types of working between signal boxes are in use on this simulation.

Track Circuit Block (TCB)

Track Circuit Block is the method of working used where all lines are continuously track circuited (or fitted with axle counters), thus providing proof that each section is either occupied or clear. There is no need, in general, for signallers at adjacent boxes to request permission for a train to pass between them. The majority of SimSig simulations work entirely under TCB regulations; see the TCB glossary entry .

Absolute Block (AB)

Absolute Block was the method of working used on multi-track lines prior to the widespread use of track circuits, and it remains in use in many areas that haven't been modernised. Signallers at adjacent signal boxes must request permission from each other to signal a train through the section between them. Proof that the section is clear where the section is not track-circuited is obtained by the signaller observing the tail lamp at the rear of a passing train.

Before allowing the signaller at an adjacent box to allow a train into the section, the clearing point beyond the box's first signal must be clear. This is essentially the AB equivalent of an Overlap, and more details are given below.

See also the Absolute Block glossary entry .

Tokenless Block (TB)

Used on some single lines, this method of working uses additional electrical interlocking between signal boxes to remove the need for drivers to carry a physical token while on the single line. Proof that the line is clear following the passage of a train is obtained by the signaller observing the train's tail lamp.

It can be considered to be a 'halfway house' between a conventional token system and full TCB.

For the purposes of this simulation, TB sections are treated as AB.

Mechanical Box Operation

The SimSig IECC platform was not designed with mechanical signalling in mind, nevertheless it has been possible to create the essential characteristics of their operation. It should be accepted that this is just a representation and it is acknowledged that there are alternative ways it could have been done. Semaphore signals are drawn as such in the simulation.

Sections of lines that are not track circuited are shown as hollow track- you will only be able to follow the progress of the train by watching the TD or F2 menu though there is an option to display these sections as lit TCs at sim launch. To aid the signaller, additional train describer berths are provided at each distant signal. The description moving from the Distant signal to the home signal indicates that the train has passed the Distant.

The Semaphore Signalling page gives a full description of the general principles of mechanical signalling, and you may wish to read that page in conjunction with this one.

Principles

Distant signals (D on the screen) are fully automatic in that you have no direct control over them, they will change between Green/Yellow depending on a set of programmed rules.

A distant will not change from Yellow to Green until all the section signals are off, except where a train has already passed it before the section is fully cleared. Distant will be replaced when a train reaches a trigger point, which will normally be the first (normally) displayed track circuit.

Home signals must be pulled off in the correct order, which is generally the direction of travel. Shunt routes pulling order may vary - see individual box notes . You will not be able to pull off a home if the next one is already off - in other words you must replace all the signals once a train has passed to be able to start the sequence again (as above signals will not TORR ).

Clearing Points

Clearing points are essentially an overlap but not interlocked to the signalling and it is possible to violate them for which there will be a penalty.

If 'Mechanical Interlocking' is not selected on start-up, the simulation simply requires the clearing point to be clear and no conflicting route set. If 'Mechanical Interlocking' is selected, the simulation also requires any points within the clearing point to be set in the correct position; this will require manual intervention. Where facing points are in the clearing point, they must be in the specified position. They can only change position when the approaching train has been brought to a stand at the home signal. The one exception is at Hilton Junction, where the junction points can be set towards Dunblane or Ladybank.

Please see also Clearing points diagrams for details of each clearing point at each box. Note that, at some locations, the clearing point extends right up to the last signal controlled by the box concerned.

Diverting Trains

Trains entering at Ladybank Main line can be diverted to Perth automatically by the imposition of the word "SHUT", "BLOK" or one of the alternatives into the TD berth at signal EB657 (first down signal). The Tay Bridge scenario will interpose the BLOK for you but you can remove and replace it as you wish.

Note that all trains will be diverted if the BLOK code is used, including those only going to Cupar/Leuchars/Tay Bridge South. If traffic is to be run to these locations, the SHUT code must not be used and the timetables of trains to Dundee and beyond manually altered to run via Perth.

ACI

ACI is provided at Perth, Dundee and Aberdeen locations and can be switched on/off per the user's preference- default at start-up is OFF.

Absolute Block Bells

The Absolute Block (AB) system in North East Scotland is intended for use in multiplayer games only and is meant as a bit of fun. As always it’s a representation of the system and not a faithful reproduction. The basic mechanics are generic to most boxes. Over the single line sections at Barnhill and Usan where there are no block instruments as such, just bells.

A Block Instrument Has 3 Positions

Line Clear (LC) / Normal (N) / Train On Line (TOL)

To get the full effect it is recommended that the bell sound is allocated to "Block Bell #1 " via the f3 menu.

Whether the bells are used, and if so whether the correct code is used, or not does not affect the performance or operation of the Sim.

Taking a representative section of Greenloaning to Blackford

A train is enroute from Dunblane to Greenloaning.

The Greenloaning Signaller needs to clear the signals to allow the train to pass.

In order for Greenloaning to clear the starter signal a "line clear" must be given by the Blackford signaller.

The process is as follows:-

Greenloaning Signaller sends "Is Line Clear?" to Blackford by 1 left click on the down block

button. This will cause the down block indication to flash at Blackford. It will also cause a bell "ding" at Blackford if the player on that workstation has set the berth occupancy message as described above.

If Blackford signaller is able to accept the train the signaller will left click the down block button causing both Blackford and Greenloaning's indication to go green (LC).

With a green "line clear" indication the Greenloaning signaller can clear the starter signal.

When the train passes Greenloanings Starter signal, the Greenloaning signaller must send "Train Entering Section" to the Blackford signaller. This is achieved by 2 left clicks on the down block button.

The Blackford Signaller must then place the block to Red (Train On Line). This is achieved by 2 right clicks on the Blackford Down Block button.

Note - Penalty Points

If the Blackford signaller fails to set the block to "Train On Line" it will automatically go to "TOL" when the train arrives at Blackford. This will result in penalty points as it reduces the safety of the system and is against absolute block regulations.

Now that the train is between Greenloaning and Blackford the Blackford signaller must clear the signals for the approaching train.

The operation is repeated and Blackford Signaller sends "Is Line Clear?" to Auchterarder Signaller. If Auchterarder is able to accept they will set the block to "Line Clear" by left clicking their down block button.

The signals at Blackford can now be cleared.

When the train passes Blackford, the signaller must send "Train Entering Section" to Auchterarder.

Auchterarder will respond by setting the block to "Train on Line"

Once the rear end of the train has passed Blackford Box (So that a real signaller could see the tail lamp) the Blackford signaller Normalises the block with a single left click.

The block section between Greenloaning and Blackford is now normal and ready for the next train.

One Signal Clearance Only

You may only clear a starter signal once for each line clear. So in our example, if Greenloaning had cleared their starter signal and then had to replace it to danger they could not clear it a second time with the same line clear. Greenloaning would need to ask Blackford to set the block to TOL and then back to LC. This resets the line clear and allows Greenloaning to re-clear the starter signal.

Clearing Points

If Blackford had given line clear while the clearing point was obstructed a violation message would have been generated and penalty points applied.

Please see the mechanial signalling section above for clearing point details.

Home and Distant Signals Must Be On

In order to give a line clear, the Home signal must be at Red and the Distant signal must be at Yellow.

Single Line Sections

Over the sections between Perth and Barnhill and Usan to Montrose North, the Red TOL part of the operation is omitted. You need to ensure you restore the indicator to White before restarting a clearing sequence.

North East Scotland Contents

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Last edited by Steamer on 06/10/2021 at 18:12