Basic Through Station
This article will show you how to do basic signalling at a through station with one track in each direction. It will be an advantage if you’ve already read the Beginner’s Guide tutorials in the Tutorials section — especially the Beginners Guide Part5 — but it’s not entirely necessary.
If you just want to place colour light signals, use the links on the right to skip down.
1 Signalling with semaphore signals
1.1 A short overview…
Traditionally, signalling on double line was done with semaphore signals. Under this sort of operation, one track carries trains one way, the other track carries them the other way, and only one train is allowed to be on the track between two stations at one time.
Because the signals were manually operated by the station’s signalman, they had to be physically connected with rods back to the station, and this meant that all the signals were located at or near to the station.
Sections of track between adjacent stations were also called “blocks”, and because the stations separated these blocks from each other, the stations themselves were called “block posts”.
1.2 Our station
So let’s start with a basic station area:
Note that we’ve designated one track as the up track, and the other as the down track. Trains on the up track are running from left to right, and trains on the down track are running from right to left. (As in any sensible country where people drive on the left :-) )
Now we need some signals. For more detail, you can read Semaphore Signals, but we’ll cover the basics here.
1.3 The Home signal
Our station probably also needs a Home signal in each direction. Home signals come before the platform, and they protect trains already sitting at the platform. They also allow trains to be more closely spaced together, because you can have one train approaching from the station behind while another sits at the platform.
In the same way we did for the starting signals, create a node before the platform. You might not want to put this immediately before the platform, however, but back maybe about 50 to 100 metres (c. 165 - 330 feet).
Now open up the Edit Node dialog box by double clicking on the signal’s node as we did before. Choose all the same settings as we did for the starting signals, except this time do not set the Section option. This is because Home signals do not control the entrance to the block section.
Once you have made sure all the settings are correct, click ok and repeat this process for the Home signal on the other line. Our station area should now look something like this, with two signals in each direction:
1.4 The Distant signal
The only signals left to add to the station are Distant signals. These provide advance warning to the driver of whether or not he/she can expect to find any of the Home signals at “stop”.
Depending on the track conditions, Distant signals are usually somewhere between 400 to 600 metres before the first Home signal. They’re not normally much further than this, because in real life the mechanical rodding that is used to control them limits how far they can be from the signalbox.
To place a Distant signal, go back along the track about 450 metres and insert a node. Then add a new signal to the node, and open up the Edit Node dialog box.
Whereas we were using the uqh signal before, we now need to find the uqd signal, which is a model of a Distant signal.
Distant signals also require some different settings to Home signals, so make sure they look like this instead:
Trains are never required to stop at Distant signals, so the Stop option should be cleared, and the Distant option set instead. Also make sure that Direction is correctly set, and that Section is cleared.
You can now repeat this process for the other track, and you’re finished!
If you set up a few stations in a row like this, trains should happily proceed from one station to the next under full operation of the signals. The Distant signals will clear only when all of the station’s Home signals in that direction are at proceed. If you have trains not scheduled to stop at the station, you should see this happening.
The Rail 3D signaller will ensure that the signals are operated when necessary and that trains do not crash into each other.
2 Signalling with colour light signals
In the real world, colour light signals aren’t limited in their placement like semaphore signals are. Since it’s all done electrically, they can be placed at regular intervals along the track to keep trains a minimum distance apart. The section in between two signals is called a “block”.
How far apart you place these signals depends on things like train speeds and types, sighting distance, curves, gradients etc. On a slower, high density suburban line, a train might pass a signal every 200 metres. But if high speeds, descending gradients and low train density are all factors, signals might be every few kilometres apart.
2.1 Back to our layout…
This is what we got up to with the semaphore signalling above:
There were also two distant signals not pictured, because they’re too far away to fit on the screen. Let’s modify the signalling on this layout to colour light signalling.
We’ll start with the Starting signals at the ends of the platforms. Open the Edit Node dialog box by double-clicking on the signal’s node, and then click Type so we can select a different signal model.
Locate the uk signal model, and click ok.
We need to make a few changes to the settings:
First, note that we’ve unticked the Controlled setting. If a signal is controlled, it means that it normally shows stop. When a train approaches it, it will look ahead to see if the track is clear, and then shows a “proceed” indication only if the track is clear. If the signal is not controlled, as in this case, the signal shows “proceed” by default unless a train occupies the block immediately after the signal.
Also note that Stop, Distant and Section are selected, and Semaphore is cleared.
Colour light signals are much easier than semaphore signals, because you only need to use one signal model, and all the signals have the same settings. Now change the Home and Distant signals so that all the signals are colour light signals with the same settings.
The station area now looks like this:
Note how the signal in the foreground is cleared, albeit only to “caution”. The signal after it is at “stop”, but that’s only because we haven’t placed any signals after it.
Insert another node a bit further down the track past the station, and place another colour light signal. Use all the same settings as all the other colour light signals thus far.
You can keep going like this along the track, placing signals on both lines at a regular interval. You may notice that the signals are very closely spaced in the examples given here — this is only so they all fit on the screen so you can see, but normally they would be further apart.
Returning to the view of the station, you can watch the signals operate as a train passes:
2.2 The overlap
The only other thing left to consider is what’s called the overlap. If there were no overlap, a train could stop just after a signal, and a following train could end up only metres behind it at the stop signal. In real life this isn’t safe, because the second train could overrun the signal and there would be a collision.
That’s why signals have an overlap. It is a short section after each signal that is part of the block before it. This means that an automatic signal might still show “stop” even though there is no train in the block immediately following it. The “stop” aspect will be caused by a train in the overlap section just after the next signal.
In Rail 3D, the overlap is the bit of track as far as the next node after the signal. At the moment, we have signals that have no nodes between them, so the overlap for some of these signals will be an entire block section. This will result in trains being spaced further apart, and also means that there will be often two red signals behind each train.
You can fix this by inserting a node just after each signal. The diagram below shows all of this:
As you can see, the block section for the signal is marked in blue. The overlap is the short piece of track extending past the next signal. The labelled signal will show stop if any train is in either the block section or the overlap.
Note: perhaps you can now see why it is called the overlap, as the overlap is also part of the next signal’s block section!
Once you’ve accomplished all of this, move on to Basic Station Crossover.
24 January 2007
MRG 03/12/2014 11:32:03