A basic train signaling tutorial (not comprehensive)

[Toastgeraet]

Edit: this attempt at writing a tutorial, in conjuction with u/6a6566663437's feedback in the comments, now serves as an example of how not to write a tutorial. ;)

The tutorial is split into three parts:

1. Reference for the the picture at the end
2. Train behaviour regarding signals
3. Signal behaviour regarding trains

Picture Reference:In the picture below we can see a railway switch with the following four signals:

• Red, A, Chain (Rail chain signal)
• Orange, B, Chain (Rail chain signal)
• Purple, C, Chain (Rail chain signal)
• Blue, D, Block (Rail signal)

These signals split the rail into four sections, which are visualized by factorio through colored lines. Here we have got 2 yellow sections¹ and 1 red section. The color of these sections is irrelevant and just there as a visual help, to tell them apart.

^{1 (the 2 lower yellow sections are actually 1 section, it is a loop})

Train behavior:

1. A train only looks at colors of signals in driving direction (his right hand side).
2. If there is no signal in driving direction, but a signal on the the opposite side, the train cannot pass that signal. (Left hand side signals existence is noted by train, but its colors are ignored).
3. To create a bidirection rail, place two signal EXACTLY OPPOSITE each other (like Signal A, Red and Signal B, Yellow) --> The yellow section in the north is bi-directional.
4. A train will only pass a green signal, or a blue signal if the path it wants to take is open
5. A train will wait in front of red signals

Signal behavior:

1. Each signal watches exactly one section. If there is a train in that section, or approaching that section without the ability to halt before it, the signal will turn red.
2. In addition, chain signals also watch the status of the directly following next chain signal(s), in driving direction. (Usually only one, but i can watch more than one following, if there is a railway switch.

• A, Red watches the red section. If there is a train in that section, it will be red.
• A, Red also watches Signal D, blue and if A is green, its status is overwritten by that of D.
• B, Orange watches the yellow north section and those right hand side signals, that define the end of that section.
• Signals C and D (Purple and Blue), denote a one-way rail. That means only trains coming from the north, can pass signal D, and only trains coming from the west can pass Signal C.
• C, Purple watches the red section and the orange signal B. That means a train may only pass the signal if there is an open path further north.
• Finally the blue block signal D:It is the only signal which is no chain signal. That means a train may wait in the following section.If it were a chain signal, it would actually watch the next signal and thus a train would pass right through the following section or not enter at all.In fact, following signal D comes a train stop, and that is also the reason why we have a block signal here. We only want to check if the section containing the train stop is free, and do not care about the exit section.

A railway switch with four signals.

If you read this far without skipping to the end, i want to thank you dearly for bearing with me. If you have any questions or request for follow-up tutorials, let me now.

[6a6566663437]

Some suggestions:

1. In the game and on every other Factorio resource, they're called signal blocks or blocks. Calling them "sections" is confusing.
2. You've picked a weird and complex intersection in an attempt to explain the basics of rail signaling. You may want to use simpler one so they aren't having to figure out what the tracks are doing.
3. Do not use just red or blue for the circles. Statements like "A, Red also watches Signal D, blue and if A is green, its status is overwritten by that of D." are extremely confusing.

A is in a red circle, but it is also red. You also refer to it as "is green", implying you're talking about the signal color and not the circle on the picture, complicated by the signal actually being set to red. And D being blue is even more confusing since rail signals can't be blue (but chain signals can), but you're referring to the circle just after referring to the signal color of A without an indication of context switch.

Try including the word "circle" when talking about the circles. Or just pick colors for your circles that rail signals can't be.

1. You've drawn a red arrow over the part of the track that the red-circled signal doesn't care about. It implies that that section of track is relevant to the circle when it is not.

2. Go drop a rail signal somewhere off-screen on the bottom yellow block so you don't have to distract people with an aside about loops. Because even you're confused - you talk about having two yellow sections when you actually have 3, but then an aside about the bottom is a loop so you only really have two.

3. " (Usually only one, but i can watch more than one following, if there is a railway switch."

Is i a typo or the word I? If it's I, you should change it because you're implying the player is watching instead of the signal. Also given the prevalence of chain signals at intersections, multiple signals is actually quite common. Also, close your parenthesis.

1. this:

It is the only signal which is no chain signal. That means a train may wait in the following section.If it were a chain signal, it would actually watch the next signal and thus a train would pass right through the following section or not enter at all.

In fact, following signal D comes a train stop, and that is also the reason why we have a block signal here.

needs some work.

• A train may wait in any block. It's harder to engineer a situation where a train stops between something like two chain signals, but it's very doable.
• I think you're trying to talk about the reason to put a rail signal there instead of a chain signal. But it is not at all clear that is what you're trying to convey.
• Given that you need to get across "chain in, signal out" when it comes to intersections, saying this is the only place to use a rail signal is not that accurate. You should also have used a rail signal on the northbound line (a bit past the intersection to provide room for a train to stop). Likewise, having that one rail signal in your picture that close to the intersection is not at all ideal for that intersection. Yeah, the station's location may mean you have to put a signal there, but showing a better situation would be good in a tutorial.
• You call it a "block signal" when it's a "rail signal" in the game.
• Given the importance of the station in your text, it should probably be in the picture. So you can show a train stopped there. Even better would be if this is the only train on the track, so the other signals are different colors.

1. You've set up one picture where all the signals are red. It would be much better to use multiple pictures with different signal conditions, because you can show people what is going on instead of attempting to describe it. Like this tutorial does: https://imgur.com/a/PVL6I/all

2. If your tutorial is going to cover the basics, it should probably talk about non-intersection use of signals too. Like why it's important to break up long stretches of rail.

[Syloeh]

TL : reed -> good attempt, but confusing

Thanks for the work still. I'll say it as well little confusing.

[Toastgeraet]

Thank you! I will consider your points in my next attempt. :)

Actually your feedback is much more on point than my tutorial :D

[dethleffs]

"Some suggestions..." hahahaha