Signals in Simutrans Extended
Signals in Simutrans Extended are a very complex subject. The signals have evolved from Simutrans Standard and have become quite different, both in functionality and appearance. A signal can be many things dependent on how the signal has been designed for the pakset and, in some cases, a signal variant that exists in one pakset does not exist in another. This signal help section will aim to describe all of the possible variants and how they would work in the game, even though a particular signal may not be in the pakset that you are playing now.
A signal in Simutrans Extended has some fundamental parameters which will be described shortly on this page. You can follow the links under the subjects to get a more detailed description.
Working methods
Since the dawn of railways, the biggest problem has always been to ensure that two trains do not crash into each other. This has resulted in the development of various safety systems, rules, technical safety instruments, etc.
Each signal in Simutrans Extended is part of a "working method", which will determine how the signal behaves and which rules and "safety systems" the train will follow after passing the signal. The working method is the most essential parameter of the signal, as all other functionality will depend on it. Different working methods represents different real life rail systems, and there are different signals available to the various working methods. Depending on the pakset, signals may be used on tram and narrow-gauge track as well as "heavy" railways. In Simutrans, drivers always obey signals, even if this could leave their trains stuck or in a dangerous position.
Whenever a train leaves a depot or platform with no signals, it will default to the Drive by Sight working method (with some exceptions).
Read more about working methods here: signals working methods
Signal boxes
A signal can't just be built as a stand-alone signal: it needs a signal box to be built. In the real world, a signal box is the shelf or the building from which the signals are controlled. Newer techniques allow for more efficient signal systems with greater numbers and more remote-controlled signals. In Simutrans, different signal boxes allow for different signals, simulating the different eras and techniques.
To build and connect signals to signal boxes, start by placing a signal box next to the track. Once the signal box is built, some signals will become visible in the rail toolbar and they will now automatically be connected to your newly-built signal box when built. If you want to connect new signals to another signal box on your map, click on that signal box and new signals will automatically be connected to that one.
Uni- and bidirectional signals
By default, signals are unidirectional: they only interact with trains they are facing, meaning that trains passing in the opposite direction will ignore the signal completely.
Some working methods, however, allow signals to become bidirectional signals, controlling traffic from both directions. To create a bidirectional signal, click multiple times with the signal building tool on the signal's tile, and the signal will cycle between being unidirectional in one way, the other way and eventually bidirectional. However, the "station signal" can only be built as a bidirectional signal.
Normal reservations and Directional reservations
Signals normally reserve track for a particular train or tram. As well as a normal reservation, it is also possible for a signal to create a directional reservation. A directional reservation reserves only the direction of the track, not the track itself. Therefore other trains can still enter the directionally reserved track, but they can only travel in the same direction as the track is reserved. When the block reservation tool, the directional reservation has the color BLUE, and normal reservation has the color RED. To see what direction the reservation is active, open the track info window.
To create a directional reservation you need to build either a bidirectional signal, or a long-block signal.
Read more about how to create directional reservations here: signals help page
Sighting distance
The train driver can only see a certain distance in front of the train. When a train is in the "drive by sight" working method, the sighting distance is the only safety feature in existence and the train is therefore required to drive slow enough to stop within the sighting distance.
The sighting distance is also used to determine the speed of a train approaching a signal. Since the train does not know the state of the next signal (except in the "cab signal" and "moving block" working methods), it must drive slowly enough to stop if the signal is at danger. To avoid this problem, pre-signals are used, which tell the driver at a much earlier point the state of an upcoming signal.
To see the sighting distance of a train, let it run in the drive by sight working method. The red reservation in front of the train will correspond to its sighting distance.
Signals max speed
At higher speeds, signs and signals get more difficult to read. Each signal has a maximum sighting speed (displayed in its window as "Max. speed") which is the maximum speed at which the train driver's human eye can read the signal. In effect, this means that a train will not pass a signal at a higher speed than the signal's maximum speed. With modern technology, cab signalling allows the signal states to be shown inside the cab of the trains, thus allowing for a much higher sighting speed.
Choose signals
Choose signals serve two functions: they will guide the train to an empty platform at the station, and they will guide a train through a station, even if the scheduled or shortest route is occupied.
To make use of this second function, you need to place an
Read more about how choose signals work on the absolute block page.
Distant signals
Distant signals, pre-signals, and repeater signals are all used only to forecast the state of the next signal. In essence, they extend the sighting distance of the following signal. These kinds of signals are not "stop signals", as most other types of signals are, therefore trains will never stop at them.
Trains might change working method when passing a distant signal though, thus reservations might still end at the distant signal. This happens mostly when the working method of the distant signal is different from the working method of the previous signal.
Read more about how to use them on the absolute block and track circuit block pages.
Multiple aspect signals
A signal may have up to five aspects, each giving a different instruction to the train driver. In addition to that, permissive signals and choose signals have specific aspects related to their functions. Different paksets reflect specific countries or signalling systems, and so certain combinations might not be available for a specific pakset.
The core function of multiple aspect signals is to combine a forecast aspect with a stop signal, thus increasing the density of the tracks. The more aspects a signal has, the smaller the blocks that can be created without compromising with lower top speeds, thus creating room for more trains on the tracks. Therefore, multi aspect signals are most useful on lines with high traffic demand.
Read more about how to use them on the Track circuit block page.
Combined signals
A combined signal is a specific absolute block signal and is an early type of multiple aspect. It has three aspects and the forecasting aspect can forecast either for the signals coupled to its own signal box, or for the following signal box, if that particular signal box is within range.
The forecasting aspect will only show clear if all signals connected to the relevant signal box are clear in the given direction.
Read more about how to use them on the absolute block page.
Permissive signals
Permissive signals are used to increase line capacity. When a train is brought to a stand at a permissive signal at danger, it may proceed beyond the signal using "drive by sight". This is only possible where the signal controls a section of straight, unidirectional track. If there are junctions, the permissive functionality is disabled and the signal functions as an ordinary signal.
Read more about how to use them on the absolute block page.
Double block signals
Double block signals will not clear until the next signal in line can clear. This is typically used when lines are branching out to two (or more) different working methods. The signal creates an absolute block type of reservation in the first block, followed by another reservation appropriate to the second block.
Read more about how to use them on the absolute block page.
Long-block signals
A long-block signal will always try to enforce a directional reservation.
Read more about how to use them on the track circuit block page.
Intermediate signals
This type of signal is a specific absolute block signal which allows an extra section to be inserted into an absolute block section between two signal boxes using semi-automatic signals without replacing the signal boxes or existing mechanical signals.
Read more about how to use them on the absolute block page.