One-way signal
One-way signal.png
One-way signals limit train movement to one direction. In the example below, the signals force the trains to move in a circle.
One-way signals in a loop
There are two main situations where these signals are more useful than simple block signals:
RoRo stations allow trains to stop at a station without reversing out and blocking the entry. This makes trains enter and exit stations more efficiently.
Double tracks allow more than 2 trains to travel without them reversing into each other. On a single-track line, if a train is present, then no trains can move in the opposite direction because they will collide at some point. On a double-track line any train can take one direction and they will never collide, meaning trains don't have to wait for other trains, and can always move on that line.
If a train arrives at the wrong side of a one-way signal, it will be blocked and immediately reverse unless player has disabled this behavior in the advanced signal options. When using one-way signals, be sure that they are all facing the correct direction. It is a good idea to watch the first train you run on the newly signaled line all the way to its destination to ensure you haven't made any mistakes.
Click on an existing two-way signal to toggle it to a one-way signal. Click on it again to change its direction (leaving it one-way); the third time will revert it back to a two-way signal.
If a train has a choice of tracks, each with a one way signal, it will pick the track heading towards its destination (i.e. it will wait until the signal on the track heading towards its destination turns green, as opposed to taking whichever signal is green if one of the signals is red). This is in contrast with two way signals.
Although the one-way (block) signal appears there is only one side of the signal facing the passing direction, technically speaking, the disappeared signal of the other side still exists and is red permanently to block the entrance from that side. This appearance is not true in the real world signalling system and is misleading for players who wish to learn the usage of the more advanced path signalling system which is more realistic and efficient in handling junction traffic.
One-way signal was first introduced to Transport Tycoon Deluxe.