Why Place Signals?
Careful placement of signals will allow you to operate complex operations involving several moving consists without incident. It is important to consider that the signals are there to protect the trains from each other, and any situation where their paths may cross should be protected by a signal.
Regional Trackside Appearance of Signals
Australian & UK signals appear on the left of the track, USA signals appear on the right. European signals vary depending on the track.
General Signal Placement Guidelines
Truly this subject can occupy a full textbook. A case in point: indeed with TRS2004 Auran released a totally separate paperback binding entitled "Signaling Guide". That being said here are a few starting principles:
- Extended sections of single line should be relieved by sections of double track or “crossing loops” that enable trains to either pass or cross each other.
- At the entrance to a section of single line there can be two signals protecting the same block, i.e. one on each track to enable faster trains to pass slower ones.
- Keep in mind that once a train passes a signal, any following train will not be permitted to pass until the first train reaches the next signal,
- ...if traffic is going to be heavy, don’t place them too far apart.
- It is recommended that you place at least one signal between each junction, and more on longer sections.
Fallible Drivers and Emergency
Being dedicated to realism, Trainz is designed to simulate real railroads, and all real railroads have drivers which are not infallible. And so in Trainz, the drivers will occasionally "pass a signal at danger", meaning they run right through a red absolute signal. Their train is abruptly thrown into "Emergency" (i.e. the air pressure line running through the train's entirety is vented, causing all individual carriages/cars/wagon air systems to engage their braking). There is nothing the user can do about this, except design a route to mitigate this fallacy. An emergency train will remain where it comes to rest for two minutes, sufficient time to recharge trainwide air pressure.
Rail End Markers
- To protect AI trains from over running terminating track, a rail end marker or buffer must be used. The take-away is that Rail End Markers are an integral part of any signaling system.
USA Signals by Auran - Special Considerations
For those modeling with the Auran USA Signals (both the 'US'/'USA' series [searchlight-style] and 'US2'/'USA2' [traffic light-style]) signals, please be aware that there are two distinct categories that behave quite differently: "Absolute" signals and "Automatic" signals.
An Auran USA Absolute signal maintains absolute control on the driver. He/she absolutely cannot pass on red, must throttle to 1/2 the speed limit on yellow, and is permitted the full speed limit on green. Absolute signals are used to maintain safe single train occupation of blocks.
An Auran USA Automatic signal however, gives credence to the driver's judgement. This indeed follows the adjective "Automatic": they look to see what the downstream signal and downstream block is doing and react accordingly, that is to say, without any other surrounding considerations a human might consider. That's why the signal condition can be augmented by the driver's judgement. For a red indication, the driver is actually permitted to pass the signal if he/she has visual line of sight verification that the train can proceed safely, but then at only half speed. Similarly for yellow, the driver can proceed at the speed of his/her discretion. Automatic signals are useful for single track end-to-end sequential blocks with little or no junctions, particularly when there is two-way trackage. They optimize a train's forward motion while preventing end-to-end collisions of sequential trains on the same track. An Automatic Signal will not protect a block from multiple train entry, so do not use them if you need to avoid this for safety.
Besides the USA, other countries with wide open single track stretches ad infinitum also adopt similar signaling conventions. Norway is such an example.
You may ask how does one tell an Absolute Signal from an Automatic Signal? Answer: Automatic signals have number boards, and Absolute do not.
Signals to Mitigate Diamond Crossing Collisions
As of TRS19 SP1 & Trainz Plus releases, N3V has no viable mechanisms to prevent the visual collision of trains at diamond crossings or slip switches. However there are effective ways to prevent this with 3rd-party asset associations, such as the ASB System asset series (Automatic Signal Block) by author "Boat".