NOTE: To make it easier to follow this article you should open SimSig, go to Options > Display and check Show track circuit breaks.
To set a route, simply follow these steps:
Locate and click on the EXIT signal or symbol marking the end of your intended route; if SimSig permits you to set that route, the flashing cursor will disappear and that section of track marking the route you have set will change colour from grey to white, extending from just beyond the entry signal to just beyond the exit signal. Any points within the route will automatically be set to the appropriate direction. Note that section of track beyond the exit signal is also set: this is the Overlap - a safety margin should a train fail to stop. The first signal will not show a proceed aspect until the entire route, including the Overlap, is clear. The end of the overlap is marked by the vertical bar in the image below.
The overlap will remain set until the train has been occupying the track circuit approaching the signal for a certain period of time, to ensure it has come to a stand. After this time, the overlap will 'release', and the track will revert to grey.
Sometimes, there are points between the signal and the end of the overlap, such that the overlap could extend in different directions. Usually, the overlap can be 'swung' in either direction, allowing additional flexibility. In this case, the points can be changed as often as desired, until the train enters the track circuit approaching the signal. The overlap will then be locked, to prevent the risk of a train overshooting the signal and running over a set of points that are in the process of changing position, which would likely cause a derailment.
Note that even if a route is set and all track circuits on the route are unoccupied, the signal may not clear immediately- see below for an explanation.
When a route is set from a signal, the signal stem is shown in white, rather than the usual grey. See the image above: the first signal has a route set from it, and the stem is white, while the second signal's stem is grey, because no route has been set from it.
If the route fails to set, check the Messages box for an explanation. Here are some of the common faults and accompanying messages:
1. "No route between selected signals". A route can only be set between two signals if it is provided for in the interlocking. Generally, you can set a route from a signal to the next signal nearby signal pointing in the same direction, however this isn't always the case. Routes generally cannot be set for long distances on the 'wrong' line, unless Bi-directional signalling is provided. Notable omissions will often be detailed in a simulation's manual, and often a small amount of trial and error is all that's necessary to learn what can and cannot be done; you'll quickly learn from experience what's allowed and what isn't.
A common reason for seeing this message is that you may have attempted to set a route to a Repeater signal instead of the next stop signal. Repeater signals are marked by an R or RR in front of them, and cannot show a stop aspect. Ignore them when routesetting and instead select the next signal which does not have an R or an RR beside it. See Signalling Display Symbols and the Signalling Principles page for more details.
2. "No overlap available". As we saw above, the track segment immediately beyond the exit signal is reserved as an Overlap in case the driver fails to stop before the signal. However, if the overlap section is unavailable, the route cannot be set until it is available again.
The most frequent cause of this message is that a section of track required for the overlap has a conflicting route set through it, or a set of points within the overlap are locked in the opposite position to that required.
In the image above, a route cannot be set to the signal circled in blue, because its overlap is already in use by the route set from the top signal.
In some cases, the overlap of the first signal cannot be 'swung' in the direction of the route you're trying to set. In this case, you must wait for the train to stop at the signal and the overlap to release before setting the route. See this illustrated example for a detailed explanation.
Routes are set from one shunt signal to another shunt signal, or from a shunt signal to a main signal, in the same manner as from a main signal to a main signal. Simply click the first signal (A), then the next signal in the same direction (B).
Trains in passenger service should not be routed from shunt signals during normal operations.
Sometimes you will find shunt signals between two main signals. In most cases you can set a route from the first main signal to the second main signal, when the shunt signals in between will clear automatically. If this isn't possible, routes must be set from the main signal to the first shunt signal, from the first shunt signal to the next, and so on.
Also note that for trains in passenger service, routes should only be set between main signals, not to shunt signals, unless absolutely necessary.
Set the route from signal A to signal B. Shunt signal 'C' acts as a running shunt, and clears automatically. Note that C's stem is grey, as no route has been set from it.
Where a main signal has a subsidiary aspect (see the signalling display page), it is usually possible to set a route from the main signal to a shunt signal. The subsidiary aspect will illuminate when a train approaches the signal.
It is not necessary to wait for a train to pass the exit signal before setting another route towards that exit signal, provided that no locked points will be required to move. In the picture below, a train has been routed from signal A to D. It is possible to set a route from B to D immediately, and B will clear as soon as the track to A, and A's Overlap, is vacated by the train. Setting a route from C to A is not possible, as it would require a set of points that is locked by the train to move. Points are locked if they are occupied by a train, or if a route is set over them. The exception is when the route is an overlap, and it's possible for the overlap to move to a different position.
In some countries, the interlocking will remember routes which the signaller has attempted to set but which aren't available, and will set them automatically when it becomes possible to do so. This is known as 'stacking'. Stacking routes is not permitted in UK signalling design, hence SimSig's UK simulations do not feature it.
To cancel a route, right-click on the entrance signal for the route you wish to cancel. A (context) menu will appear. Left-click Cancel Route, and the colour of the route segments should revert from white to grey. Notice also that the colour of the stem of the entry signal will also revert from white to grey (this is actually your most reliable indication), and the colour of the entry signal should now be red, no matter what it was before. The route is now said to be released. Releasing a route is the converse of setting a route and may be performed manually or automatically (see TORR, below). "Pulling" a route means the same as cancelling it. You should never cancel a route where to do so would cause a train to receive an adverse change of aspect, except in an emergency, or if a driver invites you to do so following a delay to his/her train at a station.
If a train already occupies part of a route you wish to cancel, cancelling the route releases only the segments up to but excluding the section occupied by the train.
Note that if attempting to cancel a route results in a flashing red entry signal, it is because Approach locking (see below) has come into action. The route will not be released until the flashing red changes to steady red.
You may wish to cancel a route because you set the wrong route, changed your mind, etc. One thing you should remember is that train drivers do not like to see a signal go back to red (or to any more restrictive aspect than the one previously displayed) in front of them, particularly if they are moving at 125 mph! To them it means that there is an emergency and they must stop the train as quickly as possible. This is termed an Adverse Change Of Aspect (ACOA). It is safe to cancel a route ahead of an approaching train as long as the next signal ahead of the driver remains unchanged, no matter what its current aspect. Once it changes from green to yellow, yellow to red or (worse!) from green to red as a result of your cancellation further down the line, the Messages box will inform you that the driver has just received an ACOA. Drivers given an ACOA will stop at the signal to report this to control, which will result in the train being stopped for several minutes. ACOAs are also penalised in the simulation score.
If the signal the driver is approaching is displaying a red aspect, you can cancel a route set from it with no penalty, since there is no adverse aspect change. Examples of this would be when the signal is approach controlled (see below).
Sometimes, a driver will contact you from a station, to inform you that his/her train is being delayed. They will invite you to replace the signal ahead to danger; if you accept this offer and cancel the route immediately, you will not be penalised.
Should you cancel a route ahead of a closely approaching train such that an approaching train incurs an ACOA, the interlocking will start a timer, known as approach locking, which gives the train time to stop. While that timer is running, the route will remain set to avoid any potential conflicts. The signal on the panel will flash red to indicate that the approach locking is in force (though the signal on the ground will show steady red). The timer duration depends on the location of the signal and the standards in force when the signalbox was designed. Typically, the timer will run for no less than 2 minutes for main signals (faster trains take longer to stop) and 30 seconds for shunt signals. For more details see Approach Locking .
Determining whether or not a train is approaching requires additional controls in the interlocking, in the form of additional wires and relays for older interlockings, or additional programming for modern interlocking. As this adds material, design and testing costs, some interlockings omit these controls, and assume that a train is always approaching. This means that approach locking will always be imposed. Additionally, approach locking is always imposed if the track approaching the signal isn't track-circuited, as there is no way of determining whether a train is approaching or not.
Note that triggering approach locking on its own does not lead to a penalty in the simulation score; only causing ACOAs does.
Some routes from signals are approach controlled. If the route set is approach controlled, you can will notice that their stem changes from grey to white but does not change their aspect, which remains red until the train is close to the signal, at which point the aspect changes to a less restrictive one (Y or G), allowing the driver to proceed.
Approach-controlled signals are usually found preceding turnouts (junctions), where the diverging speed limit is less than the 'straight ahead' limit, to ensure trains have slowed to a safe speed. See Approach Control for more details.
TORR is a means of reducing workload on signallers by automatically cancelling the route from a signal after the train passes it.
When TORR is not available, the route from entry to exit signal is not cancelled after the train passes, so must be cancelled manually by the signaller. Note that even though the route is set, once a train has passed it is 'spent' and the signal will not clear again when the train passes the signal ahead. Since a passing train leaves behind a long line of set routes needing to be cleared, the absence of TORR increases the workload on the signaller.
As TORR adds cost and complexity, many signalboxes (especially those on less busy routes) do not have TORR, and this is reflected in the simulation.
As a concession to beginner players, simulations will usually have an option to enable TORR if it isn't provided in reality. The presence and options associated with TORR will be explained in the Simulation manual . See TORR for more details.
TORR available: The train has passed the signal, and the route has cancelled behind it.
TORR not available: The train has passed the signal, but the route must be cancelled manually. The signal will not clear again when the train passes the signal ahead.
This covers the majority of routesetting operations. See this page for less common route setting operations:
Last edited by Steamer on 29/01/2019 at 20:22