Signals are the most important part of any good rail network. They prevent collisions and can be used to direct trains. There are two types of signals, two way sigils, which trains can go through both directions, and one-way signals, which trains can only go through one direction. Trains behave differently with different signals. Consider the following:
A train coming from the bottom of the picture heading towards a station left of the picture sees the two signals. If both are green, it will take the track which goes in the general direction of its destination. If one signal is red, however, it will choose the green one, even if it goes in the opposite direction it's headed.
Rule: Use two-way signals if you want the train to choose a free track, like in multi-platform stations, for example. Placing two-way signals in front of each platform will make the train choose one that's free.
But what if you want the train to choose the one that goes in the right direction, not the free one? Then you use one way signals.
A train coming from the bottom, heading left, will chose the track heading left, even if it's red.
Rule: Use one way signals if you want a train to choose the track that goes closest to its destination.
But what if the one-way signal is facing the other direction?
A train coming from the bottom of the picture will always continue on to the right.
Rule: A train will never go down a track with a one way signal facing away from it.
This can be quite handy for forcing a train into a depot
Preisgnals are a feature of TTDPatch.
The standard signals in the game are red if the track between it and the next signal, including all sidings, has a train on it. Once that train has past the next signal, the first one goes green. Pre-signals are different. The are red when all the next signals are red. This way, a train attempting to enter a station that is full will wait at the signal before the two-way signals at the start of the station, instead of waiting at the signal for the first platform it comes across.
The pre-signals in version 1.7 are different to those in version 1.8. Here we'll talk about the advanced pre-signals in version 1.8. First we will talk about the signal types, how to place the signals then some ways to use them.
There are 3 types of signals that can be used in the pre-signal set up. The top one is an entrance signal. These are placed at the entrance of a pre-signal set up and are red if all of the signals in every possible direction down the track are red, providing they are of the next two types.
The second type of pre-signal is an exit signal. It marks the end of the pre-signal block. These should usually be two-way signals so trains will "choose" green tracks over red ones. Exit signals are placed in front of the platform (assuming you're building a station) and behave like normal signals.
The third type is a combo signal. These are a combination of an entrance and an exit signal. Like exit signals, these should usually be two-way signals so trains will "choose" clear tracks. If all exit and combo signals in a pre-signal set up are red, then the entrance signal(s) leading to them will also be red. Alternatively, if all combo/exit signals behind a combo signal are red, then it too will be red.
Placing these advanced signals is easy, but you'll need the pre-signals option (-w) activated in TTDPatch. If one or more one way signals leads to one or more two way signals then the end of the line(s) or another one way signal, then the first one way signal(s) will automatically become an entrance and the two way signal(s) will become an exit. The last one way signal will not change and any one way signals facing the opposite direction to the first signal(s) will not effect any pre-signal setup.
To manually place pre-signals, simply place a signal normally on the track, then ctrl+click it once for an entrance signal, twice for an exit, three times for a combo and a fourth time to return it to a standard signal. You'll need both the pre-signals option (-w) and the exit pre-signals option (-Xw) activated in TTDPatch.
Pre-signals can be used in station entrances and anywhere you want the train to wait for a track to be clear before choosing a two way signal. With the new advanced pre-signals you can have two pre-signaled entrances to your station, but when one half of the station is full, the other half can still be used by trains coming from either entrance, as represented in picture 1. In the top of the two, you see there are two trains entering the station at once. Take note of what type of pre-signal is placed where.
In the picture 2, the top two station platforms are full so the train goes through the combo signal into the lower pre-signal set up and chooses a free platform.
There is a problem with this set up. If only the top three platforms are occupied, the fourth exit signal will be green, and thus so would the combo and both entrance signals. If a train comes through the upper entrance signal, the lower entrance signal will still be green until the train passes through the combo signal. Another train can come through the lower entrance and beat the first train to the free platform. This leaves the first train waiting at a red signal for the bottom two platform to clear. It is too far in the set up to use top two platforms should either one become free first. This is shown in the third picture.
I've also seen trains get confused in these advanced pre-signal blocks and try to go the wrong-way past a one-way signal and get stuck. With both of these problems, all you can do is keep a watchful eye over the station and tell trains to reverse/ignore signal when they get stuck (Use extreme caution when telling a train to ignore a signal. Make sure there are no trains on the other side of the signal). I still think the advanced pre-signals are worth the effort as these two problems rarely occur.
Yet another great feature in TTDPatch is New Non-Stop Handling. This makes all orders automatically non-stop and all non-stop orders mean don't-stop. So a train with the order "Go to Station X" will go non-stop to Station X, while a train with the order "Go non-stop to Station X" will go through Station X but not stop at it.
Using this feature you can make a train take a certain path to get to its destination by telling it to go though a check-point. A check-point is just a one square long station, nothing more.
Treat check-points as you would buoys, except put non-stop in the orders. Also, when using check-points it's suggested that you have the "selectgoods" tag (-G) enabled so cargo doesn't go to the check-points.
The rail-road crossings in TTD are death-traps. You'll loose a thousand times more vehicles on them then anywhere else. In the eyes of the train drivers, road vehicles must be mobile speed-humps.
The lights don't come on early enough and even the fastest of road vehicles can't clear the way in time for a maglev or monorail. Road vehicles can break-down on the crossing, a train comes along and bye-bye road vehicle. When there are two tracks next to each-other, road vehicles waiting for one crossing queue across another, a train comes along and you have a dead driver.
The best way to avoid the trampling of your trucks is to build bridges or tunnels. Keep them away from your murderous maglevs. This way there is no crossing and your road-vehicles are spared.
If your road-vehicles are destroyed (or any of your vehicles), all your rating in near-by stations plummet to 0. You should launch a large ad campaign in all near-by towns.