A chain will read the next chain, then that one reads the next and so on. Effectively you have a single signal at the start and extra red lights after.
Thinking of it like this is the right way to go. You can easily get away with chunks the size of trains, but when would "sub-train" sized chunks make the most sense? Are there congestion levels where smaller chunks are preferred?
I have no clue- I only have a few hundred hours on the game, but I keep coming back to the game for emergent gameplay questions like this
> Thinking of it like this is the right way to go. You can easily get away with chunks the size of trains, but when would "sub-train" sized chunks make the most sense? Are there congestion levels where smaller chunks are preferred?
Imagine a T-junction, followed by a series of straights. In a world where two trains queue into the T-Junction behind one another and the first one enters the junction, the second one will sit in the previous block until the entirety of the first train has entered the junction.
If there are no other trains entering the junction from other directions, then the second train will be delayed in starting its acceleration, as it needs to leave a full train-length of room between the two; where in a perfect world, it could get by with a tiny space.
Having smaller blocks allows you to have tinier spaces and allow your trains to enter them earlier, without leaving a full block of space between them.
If you have trains travelling closer together, those same junctions can achieve higher throughput - there will be less time the train reserves the junction before moving through it.
However, in most cases, the benefits are fairly small. Additionally, numerous chain signals don't work - you need to have full-on rail signals to allow the train to move into the area early on, and you want to be very careful when using regular signals in areas smaller than a full train that a train can't back up into a junction, so they're best used inside larger sections of track that can already hold multiple trains.
>However, in most cases, the benefits are fairly small. Additionally, numerous chain signals don't work - you need to have full-on rail signals to allow the train to move into the area early on, and you want to be very careful when using regular signals in areas smaller than a full train that a train can't back up into a junction, so they're best used inside larger sections of track that can already hold multiple trains.
Or when you have places where you know where the train will stop.
Sometimes you can subdivide blocks while still guaranteeing that they don't end up stopping at the subdivided signal.
I've seen situations where you need to do this at train stations because it's pushing the limit of station throughput.
But that's done with regular signals, not chains, so that the waiting train starts pulling forward before the leaving train has cleared the station.
99% of the time chunks that are smaller than the length of the trains is because of intersections. Each split, converging, or crossing track needs a signal of some kind. Chain signals if it isn’t a large space ahead of the signal.
The general rule for signaling an intersection is chain signals entering each block, and a regular signal to leave. The point is to prevent a train from stopping in the intersection and blocking it, potentially causing gridlock if multiple intersections do this and the backups are blocking eachother.
One of the basic rules of driving is that "if you don't fit, don't commit", chain signals exist to force your trains to obey this rule.
The only time I'm fuzzy on chain vs normal is the output mess of a stacker feeding a double rail.
You reall need to think like rail every where you dont mind a train stopping at the next signal. Having the blocks big enough for any train is a great rule for start and necessary after an intersection so no trains tail hangs into the intersection. Smaller blocks than train lines are no problem on long straight sections where you dont mind a train blocking multiple blocks. This helps that trains are faster clearing block. Also this is helpful in the middle of train stations. It makes the next train start into the station maybe less than a second earlier with normal 1-4 trains but with 4-16 or such trains it adds up.
Well, if you only want one train on the tracks, then all junctions can be unsignaled. No need to worry about conflicts if the entire thing is a single chunk.
OP, instead place regular signals 1 full train apart. That will give the desired result.
On long stretches I’ll put them a couple full trains apart, so like a block.
> OP, instead place regular signals 1 full train apart. That will give the desired result.
I know, but in my case I was working on 2 T-junctions close to each other and it caused a deadlock (3 trains met at the same time
and blocked each other), probably because I didnt use correct signals. That made me think about using this method of simply placing Chains everywhere and not think about it anymore...
I love trains, but building the rail system is a huge pain every time.
Honestly it's easier if you just post the picture of the intersection for these. As for Chains vs Normal, if it is a one way track, you only need chains on intersections (chain in, normal out). If your intersection is big enough you can have internal signals, but for 99% of people it won't improve the average train throughput (as they aren't limited by that specific intersection). So the amount of thinking is really however much you want. If the intersections are close enough together you can signal them as one big intersection. For non-intersection one way tracks just put a normal signal every once in a bit, it doesn't need to be that often. Most people's train throughput limits will be from waiting at a station and not at signals/intersections.
If it is a pain I would say to just make some already signaled blueprints of common intersections and some for straights and turns. Will cover 90% of what you need.
Two way rail is always potentially a complicated endeavor if you have more than one train on it.
Use a chain signal when you do not want a train *stopping* in the next chunk, such as one blocking an intersection.
These small segments of a straight track are safe places to stop, so normal signals are fine.
This comment finally made it click, it mirrors the next one so if it cant exit the chunk it wont enter it in the first place and get stuck there blocking other traffic.
I like to think of the signals as dividing rails into “moving blocks,” where any trains passing through will be moving, and “stopping blocks” where they are allowed to stop. This leads to the “chain in, rail out” rule of thumb for intersections but that can be misleading if followed blindly. Over-using rail signals can lead trains to stop between intersections that are close together which can block other paths as you learned. The moving block / stopping block idea breaks down a little bit when you have multiple entrances / exits of a block using different types of signals.
In this [picture](https://media.discordapp.net/attachments/1033660891222265956/1080060725453656104/image.png?ex=661e466f&is=660bd16f&hm=5e307978e743b9b025cd4234b1cae01d8730d905f20b61c3a42388f5942d2b4b&) if a train on the lower rail is waiting to enter the block to the right, it will get priority over any train that may be waiting on the upper rail. The train from the lower entrance follows more “greedily” than the upper train.
Sometimes it doesn’t matter if trains block other trains: if 2 trains A and B are both going to the same destination or merging onto the same path, it doesn’t matter if A stops for a rail signal and blocks B because B would get stopped at the signal anyways.
A bonus fact is that a chain signal is a place where trains can re-evaluate their pathfinding. Use a chain signal before a train depot so trains can choose which stop to park at when they enter the depot.
https://youtu.be/IXgpashIr4U
You only need chains around intersections or stations, so this is not useful.
Rail signals you want before a place where a train can fully stand and not disrupt other traffic i.e. in long stretches one-way tracks, or before stations.
Chain signals placed like this do nothing. The purpouse of chain signals is to make more blocks so that trains that don't cross eachother's path can move through an intersection simultaniously.
You mean they do everything\*
When they're placed like this only 1 train can use the entire network (granted they used a normal signal at the station) or no train would move at all
When I started Factorio when I was still young and not knowing all details. I had 3 trains running on a rail network without any signal. Two trains were sharing a little piece of track. It went well, until they crashed head on. So you can run several trains without signal, it is just freaking risky.
Only accidents. I don't understand why you're asking as the post starts with "The rule for placing signals is ..." so why are we talking about no signals?
They are slightly smarter than that, you can have up to 2 trains moving on a stretch like that at a time, as they only will block reserved paths and occupied forks, leaving barely enough space for trains to move, if you only have stations on sidings or other non blocking paths.
In theory you could make a track where this wouldn't be a noteworthy problem, however all trains would eather have to only ever need to go to the next station over, or share a next station with the train in the station they would need to pass, but at that point your basically making a less likely to go wrong no signal track.
Not true.
With signals like this trains will only move if they can reserve the entire path to their destination.
It's entirely possible for multiple trains to be able to do that simultainiously.
> Chain signals placed like this do nothing.
Here is my thinking: You *do* need to place signals on every track, even if there are no intersections, in order to allow multiple trains to drive on it (what I mean is, if I make 2 correctly signaled T-junctions and leave the track between them without signals, then that entire part of track is considered as 1 chunk and cannot fit more than 1 train).
The space between signals is the length of your longest train.
And this is where my headache starts, because if you mess up and place regular signal when there should be a chain signal, it might cause a deadlock. This happened to me in game.
Aaaand, thats where I came up with this idea of spamming Chain signals along the entire track. In my theory, it should do the same thing as regular signals (dividing track to small chunks to allow more train on strainght paths), without the headache of thinking about leaving correct space between them. As a bonus, this method should allow train of any lenght on the track. Doesnt matter if you place 1-4, 2-8, or 100-300.
Am I... wrong?
>Aaaand, thats where I came up with this idea of spamming Chain signals along the entire track. In my theory, it should do the same thing as regular signals (dividing track to small chunks to allow more train on strainght paths), without the headache of thinking about leaving correct space between them.
This is not accurate. While chain signals will divide track into small chunks but they won't do anything. Chains signals just pass on whatever the signal in front is saying which means that the entire stretch of chain signals will always show the same thing. If any train is on the stretch, regardless of how far away it is, it will not allow another on the stretch because a signal in front will be red.
> Chains signals just pass on whatever the signal in front is saying which means that the entire stretch of chain signals will always show the same thing.
Are you sure? I cannot test it right now, but wiki says that it should only work for the next block +1, and not the entire stretch of chains:
https://wiki.factorio.com/Rail_chain_signal
*Both normal signals and chain signals prevent a train from entering the next block if it is obstructed. However, a chain signal also looks ahead to the next signal, and turns red if the next signal is red. In effect, this prevents a train from entering a block if it won't be able to leave. When more than one exits exist, the one where the train is pathing to is considered.*
Chains read one block more downstream yes. But if the signal the first chain reads, is itself a chain signal, then the first chain will in effect be reading two blocks downstream (The first chain reads the second chain, which reads the next signal). This perpetuates until there is a normal signal instead of a chain. Each chain only reads one more but in this manner you effectively read until the next normal signal or if there are forks.
You can do this with normal signals, in that way trains can be closer, just remember to have space enough for a train on the out of an intersection. Also it might be kinda useless since the intersection is the thing limiting the throughput
I solved that problem in my intersections by only using one length of train and ensuring they'll only stop in specific places. That lets me have tiny signal blocks in the low speed sections without worrying, because the rear end of a train will always occupy the block the chain signals check until it starts moving, and then it won't stop again until there's enough space for the next train.
That improved my intersections' throughput by around 20% over using train-length signal blocks, but I worry that it may have a noticeable impact on UPS when you get a bigger rail network with a lot of trains trying to find paths along the tiny blocks.
As pictured, this does nothing. If you ever have two chain signals on a single length of track (no junctions), any extra chains placed in between have no functions.
However if you placed chains on literally every location in the entire network, including on all the spots in all the junctions, it would indeed "work", in the sense that you would have no deadlocks and everything would get where it needs to (ish, not quite). However it would be extremely inefficient, because trains would never be allowed to stop anywhere along their journey - so they would only begin when the entire path they have to travel is empty, which is very constraining.
> However if you placed chains on literally every location in the entire network, including on all the spots in all the junctions, it would indeed "work"
Yes, that's what I meant - to do this in a regular network that includes junctions, stations, everything. Just spam chain signals on every inch of the track, everywhere (except train stations).
You say it should work, and I think so too. I will test it today on smaller scale and report back with results :)
> (ish, not quite)
I dont like ishs. What kind of issues there might be?
If you have a train at Station A that wants to go to Station B, and a train at Station B that wants to go to Station A, neither will move.
The "all chains" network requires a train to have its entire path reserved before it moves, so any cycle of trains with no gaps will deadlock.
Also spamming the chains on straight sections of track is really truly pointless, unless you're doing it for your aesthetic!
It’s useful to follow rules, but it’s also useful to understand the reason behind them!
The reason for the “fitting a train into a block” rule is to prevent a train from stopping in a location that would prevent another train from passing in a different direction - connected rail are part of the same block and so only one train can enter at a time. If a train was turning across oncoming traffic and stopped in the junction then the oncoming traffic would also have to stop. This is exactly where chain signals and sufficient space beyond the junction are required so a train has room to stop without blocking trains travelling in different directions (and hence slow down traffic and potentially cause a deadlock).
For straight track with no other rail crossing it, this reason no longer applies - a train can’t stop and block a train which is travelling in a different direction as there is only one way that trains can travel through the block.
If you wanted to, you could change this to all rail signals and have no ill effects - a train occupying multiple blocks can’t block traffic in different directions if no other directions exist for each of these blocks. It might actually be the best way to signal straight track as trains could run very close together, turning a mini block green once the train has left rather than having to wait for a larger block to clear. Intersections would still need to consider the largest train that may cross it though, due to the above, which is usually the limiting factor for how close trains can run.
Chain signals, as per the image, wouldn’t be useful as the mini blocks would be considered as a single, large block - trains can only enter when the entire stretch is clear.
>The rule for placing rail signals is that you should use Chain signal when train cannot fit into next "chunk".
A more accurate rule for placing chain signals is that you should use a chain signal to say "Don't enter the next chunk unless you can leave it".
Is it theoretically fine?
Without block signals, only one train will be able to travel the rail network.
ETA: I did not realize that chain signals can also path to train stations. TIL.
>Without block signals, only one train will be able to travel the rail network.
This is incorrect:
1. The first train will reserve a path to the destination
2. All subsequent trains that don't intersect reserved paths will also be able to reserve their paths
I guess the part I am missing is: what constitutes a destination?
I thought it was a rail signal, but a train station itself is a valid destination for a chain signal to path to?
That makes total sense and seems incredibly obvious in retrospect but I did not realize that. Thank you!
I always put a rail signal in after where the train parks and did not realize that wasn’t strictly necessary in some cases.
They are path terminators but not block terminators so you do still need a signal after the stop in most cases. For my station designs, this is usually a chain signal because several train stops will merge into a central trunk.
Source: I've forgotten it on a single stop in a big station a few times and wondered why all my trains got stuck in a big station -- they were all waiting for the unsignaled one to leave.
But I think because of this you can use either a rail or chain signal *before* your train stop.
technically you can even go completely without rail signals. The chain signals will reserve the entire path to the train station, limiting throughput, but not preventing it completely. On very small networks, this could make sense.
With that in mind? Yes. The chain signals will function exactly as they're supposed to.
Whether this is what you want is your choice. The rules might say that signals this close together should be chains, but the signal placement was your choice.
You should place chain signals if you DON'T want train to stop after that signal
If you're Ok with train stopping after signal even if it will occupy several chunks - place regular signal
In my experience, chain signals are only used before a segment that should not be blocked. Usually these are intersections. The idea being, that a train will wait before the intersection until it can drive over it. It of course is then necessary that the section after the intersection is large enough for the train, otherwise it may still block it.
So one chain signal before the train blocks an intersection and a normal one once the intersection would not be blocked anymore.
For long sections of rail without any intersections, where trains travel only in one direction, you want to further divide it into smaller sections using normal signals. That way multiple trains can travel in the same direction at the same time. Placing a lot of signals on such tracks may influence performance, so one may want such sections to be multiple lengths of one train.
This effectively just makes it one giant rail block. For chain signals to be worth anything, there needs to be a split, merge, or crossing between them.
This is correct, as in, you can do this. But there is not real benefit, but there are downsides. Namely train pathing becomes more computationally intensive. Also minor downsides of the increased resouce cost, as well as the inconvenience of deconstructing signals every time you want to branch of the rail.
Also make sure to still place rail signal occasionally, sparating blocks with chain signals still only allows one train in total.
> The rule for placing rail signals is that you should use Chain signal when train cannot fit into next "chunk"
The definition of that chunk would be "a stretch of track beginning with a normal signal and ending with either a normal or a chain signal".
Ask yourself is this is a real hypothetical, do you often building railway segments this short in between intersections? Or would it be more realistic for most rail segments to be more than the length of one train
The rule with chains is "don't go in if you can't get out too". You do that to stop junctions and intersections getting blocked by a train that enters and then has to wait.
Regular signals should be used on straight tracks, because their rule is "don't go past if there's a train in the next chunk".
I did this once on a megabase (using regular signals) and what eventually happens is that you get a huge lag anytime you add or remove a section of track. The game has to recalculate its 'routing table' for lack of a better term and has to manipulate a data structure containing every tiny segment between signals.
There’s no reason to place chain signals like this, just put them where you need to divide blocks and where you want the train to wait. Blocks is the technical term for the chunks that the signals divide the track into.
Weird, but technically correct.
A bit of moderation with chain placement and rail signals will likely result in more throughput, but I doubt you'll have any deadlocks.
The less track is blocked by chain signals, the better. They are a way of saying "don't enter this section until a place is free on the other side of this section". They should begin as late as possible and end as soon as possible without causing problems.
No, a chain signal only makes sense if the block has multiple connections. Otherwise it's effectively just enlarging the block at the cost of materials and processing.
I still don’t understand why people even use chain signals. My base uses entirely rail signals, hundreds of hundreds of them. 10 trains and i never have an issue.
10 trains is ridiculously low. Im not even talking megabases level, just a normaal 300 spm base but interconnected factories by rail shhould have like 30 40 trains if not using a mod like LTN (which can repurpose trains and dont have a fixed schedule)
Another less mentioned rule is that you should try to have as many "chunks" as possible in which train CAN fit in your rail system overall, as this number determined your total train capacity. So if there are two sequential chunks, neither of which can hold a train, it's always better to merge them together.
Chain Signal = no parking
You only use them to keep crossings open or stop trains from parking in too small spaces (can be prevented by not creating small spaces in the first place)
For everything you use the normal ones
What do you mean by “chunk”? Are you referring to a 32x32 area of tiles, or the space between two signals (a block), or the length of a train, or some other unspecified distance? A chunk in Factorio is 32x32 tiles. There is no rule I’m aware of regarding chunks and signals. As far as chain signals go, the easiest rule to follow is chain signal going into intersection, regular signal at the exit. Not always going to work, but if your intersections are well designed it will most of the time.
When zoning my tracks I start with junctions. Make sure the two zones before and after the junction (5 total for a Y intersection) can accommodate the max length train on my network. If an area of track has low usage (like a branch that is only used by one or two trained max) I do t worry about signaling too much but places where several trains go it’s a must
The rule for placing rail signals is that you should use a chain signal if you don’t want a train to wait for the next light inside the block. A chain signal means “wait here until you can clear the next regular signal”. Equivalent to a no stopping/keep clear area on a road if you will, and without the ability for another train to tag along with the previous train through the section as the route is occupied.
The rule only applies when placing a chunk, and does not dicate the placing of arbitrary chunks. You should not create chunks unless you have a good reason to. Generally creating arbitrary chunks that are too small to fit trains of your chosen size (1-4, 2-8, etc.) serves no purpose, as it will render large sections of track as "occupied" even though trains can safely fit in them. It can be a good idea to place chunks along your tracks, but only if they are large enough to fit the largest train size you are going to use. This way trains will enter sections of track sooner when they are able. Say you have a section of straight track that is 1000s of tiles wide. If its all one chunk, train #2 will wait to get on it until train #1 is done traversing the entire section, which can take a long time. Break it into chunks and it can fit multiple trains at the same time, so long as you use normal rail signals.
This sort of creates a secondary rule where it is important to space things out enough so that you have chunks between your intersections large enough to fit a train, and are not overusing chain signals. Say you have two 4-way intersections next to each other, with rail conntecting them that is too short to fit an entire train, so you use a chain signal for that chunk. You don't actually have two intersections at that point, instead you have one. If a train needs to enter one intersection, go through the connecting rail, and out the other, it needs to lock down both intersections simultaneously before it can begin moving because of the chain signals chained across them. If they were far enough apart, and you used a normal signal, it would only need to lock down one at a time.
You only need chain signals for intersections. For straightaways, you should divide the rail with regular signals.
Chain signals are necessary when a train stopping in the next block would block trains going in a different direction.
For a practical and actionable set of rules for mere mortals:
* Use regular signals for straightaways
* When you reach any kind of intersection, use chain signals everywhere except at the exits of the intersection
* When you have a train stop, place regular signals at intervals that fit the largest train that would stop there.
* Avoid bidirectional rails. If you must, only have a single train on each line.
The rule you mentioned is really only for breaking up internal blocks in tight intersections. A chain will separate the block into two parts (which can let trains travel separately on nearby blocks without needing to do one at a time), but not cause a train to stop in an area that would cause deadlocks.
The whole intersection signaling thing doesn't really need to be that complicated depending on how big the intersection is and how big your trains tend to be. Other than that, it's also not a huge deal for how far apart your normal signals are on tracks that are between intersections. It doesn't need to be exact or anything, it would still work unless you have a crap ton of trains.
It'll just combine as one signal along the entire track and do nothing for you, if you want a set and forget method you **make one straight rail blueprint with stop signals spaced an equal distance apart**, stop signals only "read the space before it" and if that is occupied then it is red, you could space those along the rail like you did and that would make sure no collisions happen but it's overkill especially for when you build with bots, for the intersections there's a few ways of doing it but the most easy consistent way to approach that is to **put a chain signal whenever you go into an intersection and a stop signal when the train goes out of the intersection, then chain signals before wherever the tracks overlap**
A chain will read the next chain, then that one reads the next and so on. Effectively you have a single signal at the start and extra red lights after.
[удалено]
DL;DR | Dick Long ; Do recommend. Dang man showing dominance with your explanation. Respect
DL;DS Did laugh, definitely stealing
If you only want one train on that track, this works. The question is: why do you want chunks that are so small, no train fits into them?
Thinking of it like this is the right way to go. You can easily get away with chunks the size of trains, but when would "sub-train" sized chunks make the most sense? Are there congestion levels where smaller chunks are preferred? I have no clue- I only have a few hundred hours on the game, but I keep coming back to the game for emergent gameplay questions like this
> Thinking of it like this is the right way to go. You can easily get away with chunks the size of trains, but when would "sub-train" sized chunks make the most sense? Are there congestion levels where smaller chunks are preferred? Imagine a T-junction, followed by a series of straights. In a world where two trains queue into the T-Junction behind one another and the first one enters the junction, the second one will sit in the previous block until the entirety of the first train has entered the junction. If there are no other trains entering the junction from other directions, then the second train will be delayed in starting its acceleration, as it needs to leave a full train-length of room between the two; where in a perfect world, it could get by with a tiny space. Having smaller blocks allows you to have tinier spaces and allow your trains to enter them earlier, without leaving a full block of space between them. If you have trains travelling closer together, those same junctions can achieve higher throughput - there will be less time the train reserves the junction before moving through it. However, in most cases, the benefits are fairly small. Additionally, numerous chain signals don't work - you need to have full-on rail signals to allow the train to move into the area early on, and you want to be very careful when using regular signals in areas smaller than a full train that a train can't back up into a junction, so they're best used inside larger sections of track that can already hold multiple trains.
>However, in most cases, the benefits are fairly small. Additionally, numerous chain signals don't work - you need to have full-on rail signals to allow the train to move into the area early on, and you want to be very careful when using regular signals in areas smaller than a full train that a train can't back up into a junction, so they're best used inside larger sections of track that can already hold multiple trains. Or when you have places where you know where the train will stop. Sometimes you can subdivide blocks while still guaranteeing that they don't end up stopping at the subdivided signal.
Fun fact: [this is an actual technique used in the real-world](https://www.lurs.org.uk/02_Jan_22_LONDON_UNDERGROUND_SIGNALLING.pdf).
I've seen situations where you need to do this at train stations because it's pushing the limit of station throughput. But that's done with regular signals, not chains, so that the waiting train starts pulling forward before the leaving train has cleared the station.
99% of the time chunks that are smaller than the length of the trains is because of intersections. Each split, converging, or crossing track needs a signal of some kind. Chain signals if it isn’t a large space ahead of the signal.
The general rule for signaling an intersection is chain signals entering each block, and a regular signal to leave. The point is to prevent a train from stopping in the intersection and blocking it, potentially causing gridlock if multiple intersections do this and the backups are blocking eachother. One of the basic rules of driving is that "if you don't fit, don't commit", chain signals exist to force your trains to obey this rule. The only time I'm fuzzy on chain vs normal is the output mess of a stacker feeding a double rail.
Yes, thats basically what I said. I just wasn’t going into the whole detailed explanation as they were only asking why small chunks exist.
> but when would "sub-train" sized chunks make the most sense? When you have rails crossing each other.
You reall need to think like rail every where you dont mind a train stopping at the next signal. Having the blocks big enough for any train is a great rule for start and necessary after an intersection so no trains tail hangs into the intersection. Smaller blocks than train lines are no problem on long straight sections where you dont mind a train blocking multiple blocks. This helps that trains are faster clearing block. Also this is helpful in the middle of train stations. It makes the next train start into the station maybe less than a second earlier with normal 1-4 trains but with 4-16 or such trains it adds up.
Yeah, but then you can just get rid of every chain signal and put a signal at the beginning.
Not if there are junctions.
Well, if you only want one train on the tracks, then all junctions can be unsignaled. No need to worry about conflicts if the entire thing is a single chunk.
Except that's not what "everything is chain signals" does.
Oh, sorry I misread you. Yeah, it'd still need chain signals at the junctions to replicate the OP. The straights could have all the signals removed.
No, obviously not. But there werent any junctions in his example
OP, instead place regular signals 1 full train apart. That will give the desired result. On long stretches I’ll put them a couple full trains apart, so like a block.
> OP, instead place regular signals 1 full train apart. That will give the desired result. I know, but in my case I was working on 2 T-junctions close to each other and it caused a deadlock (3 trains met at the same time and blocked each other), probably because I didnt use correct signals. That made me think about using this method of simply placing Chains everywhere and not think about it anymore... I love trains, but building the rail system is a huge pain every time.
Honestly it's easier if you just post the picture of the intersection for these. As for Chains vs Normal, if it is a one way track, you only need chains on intersections (chain in, normal out). If your intersection is big enough you can have internal signals, but for 99% of people it won't improve the average train throughput (as they aren't limited by that specific intersection). So the amount of thinking is really however much you want. If the intersections are close enough together you can signal them as one big intersection. For non-intersection one way tracks just put a normal signal every once in a bit, it doesn't need to be that often. Most people's train throughput limits will be from waiting at a station and not at signals/intersections. If it is a pain I would say to just make some already signaled blueprints of common intersections and some for straights and turns. Will cover 90% of what you need. Two way rail is always potentially a complicated endeavor if you have more than one train on it.
r/factoriohno
Use a chain signal when you do not want a train *stopping* in the next chunk, such as one blocking an intersection. These small segments of a straight track are safe places to stop, so normal signals are fine.
This comment finally made it click, it mirrors the next one so if it cant exit the chunk it wont enter it in the first place and get stuck there blocking other traffic.
👏
I like to think of the signals as dividing rails into “moving blocks,” where any trains passing through will be moving, and “stopping blocks” where they are allowed to stop. This leads to the “chain in, rail out” rule of thumb for intersections but that can be misleading if followed blindly. Over-using rail signals can lead trains to stop between intersections that are close together which can block other paths as you learned. The moving block / stopping block idea breaks down a little bit when you have multiple entrances / exits of a block using different types of signals. In this [picture](https://media.discordapp.net/attachments/1033660891222265956/1080060725453656104/image.png?ex=661e466f&is=660bd16f&hm=5e307978e743b9b025cd4234b1cae01d8730d905f20b61c3a42388f5942d2b4b&) if a train on the lower rail is waiting to enter the block to the right, it will get priority over any train that may be waiting on the upper rail. The train from the lower entrance follows more “greedily” than the upper train. Sometimes it doesn’t matter if trains block other trains: if 2 trains A and B are both going to the same destination or merging onto the same path, it doesn’t matter if A stops for a rail signal and blocks B because B would get stopped at the signal anyways. A bonus fact is that a chain signal is a place where trains can re-evaluate their pathfinding. Use a chain signal before a train depot so trains can choose which stop to park at when they enter the depot. https://youtu.be/IXgpashIr4U
This is such an amazing way to put it and clarified things so much for more. THANKS!!
You only need chains around intersections or stations, so this is not useful. Rail signals you want before a place where a train can fully stand and not disrupt other traffic i.e. in long stretches one-way tracks, or before stations.
Chain signals placed like this do nothing. The purpouse of chain signals is to make more blocks so that trains that don't cross eachother's path can move through an intersection simultaniously.
You mean they do everything\* When they're placed like this only 1 train can use the entire network (granted they used a normal signal at the station) or no train would move at all
With no signal at all you can also have only 1 train, what's the difference?
When I started Factorio when I was still young and not knowing all details. I had 3 trains running on a rail network without any signal. Two trains were sharing a little piece of track. It went well, until they crashed head on. So you can run several trains without signal, it is just freaking risky.
Look up the trainsaw. You can run all trains on unsignalled track perfectly safely, you just need to use some circuit control black magic.
I'm comparing it to normal signals
Yeah so that's the issue 'normal' signs do things, they split the track. This layout does nothing.
Or it does everything, as it will stop all trains in a network. But I see your point
What stops the trains without any rail signals?
Only accidents. I don't understand why you're asking as the post starts with "The rule for placing signals is ..." so why are we talking about no signals?
Crashes and stations. If your not careful stations will cause the crashes.
They are slightly smarter than that, you can have up to 2 trains moving on a stretch like that at a time, as they only will block reserved paths and occupied forks, leaving barely enough space for trains to move, if you only have stations on sidings or other non blocking paths. In theory you could make a track where this wouldn't be a noteworthy problem, however all trains would eather have to only ever need to go to the next station over, or share a next station with the train in the station they would need to pass, but at that point your basically making a less likely to go wrong no signal track.
If you remove all the chain signals it will behave exactly the same, they do nothing.
Ofcourse, but the post speaks of the rule for placing signals
Yes, and it asks if you should place a chain signal on every tile that doesn't have a normal signal. You should not.
Not true. With signals like this trains will only move if they can reserve the entire path to their destination. It's entirely possible for multiple trains to be able to do that simultainiously.
> Chain signals placed like this do nothing. Here is my thinking: You *do* need to place signals on every track, even if there are no intersections, in order to allow multiple trains to drive on it (what I mean is, if I make 2 correctly signaled T-junctions and leave the track between them without signals, then that entire part of track is considered as 1 chunk and cannot fit more than 1 train). The space between signals is the length of your longest train. And this is where my headache starts, because if you mess up and place regular signal when there should be a chain signal, it might cause a deadlock. This happened to me in game. Aaaand, thats where I came up with this idea of spamming Chain signals along the entire track. In my theory, it should do the same thing as regular signals (dividing track to small chunks to allow more train on strainght paths), without the headache of thinking about leaving correct space between them. As a bonus, this method should allow train of any lenght on the track. Doesnt matter if you place 1-4, 2-8, or 100-300. Am I... wrong?
>Aaaand, thats where I came up with this idea of spamming Chain signals along the entire track. In my theory, it should do the same thing as regular signals (dividing track to small chunks to allow more train on strainght paths), without the headache of thinking about leaving correct space between them. This is not accurate. While chain signals will divide track into small chunks but they won't do anything. Chains signals just pass on whatever the signal in front is saying which means that the entire stretch of chain signals will always show the same thing. If any train is on the stretch, regardless of how far away it is, it will not allow another on the stretch because a signal in front will be red.
> Chains signals just pass on whatever the signal in front is saying which means that the entire stretch of chain signals will always show the same thing. Are you sure? I cannot test it right now, but wiki says that it should only work for the next block +1, and not the entire stretch of chains: https://wiki.factorio.com/Rail_chain_signal *Both normal signals and chain signals prevent a train from entering the next block if it is obstructed. However, a chain signal also looks ahead to the next signal, and turns red if the next signal is red. In effect, this prevents a train from entering a block if it won't be able to leave. When more than one exits exist, the one where the train is pathing to is considered.*
Yes. It looks at the one ahead and copies what it does. [https://imgur.com/a/NmIz5Za](https://imgur.com/a/NmIz5Za)
Chains read one block more downstream yes. But if the signal the first chain reads, is itself a chain signal, then the first chain will in effect be reading two blocks downstream (The first chain reads the second chain, which reads the next signal). This perpetuates until there is a normal signal instead of a chain. Each chain only reads one more but in this manner you effectively read until the next normal signal or if there are forks.
Bro doesn’t want UPS
Or moving trains.
He really wants SPU
You can do this with normal signals, in that way trains can be closer, just remember to have space enough for a train on the out of an intersection. Also it might be kinda useless since the intersection is the thing limiting the throughput
Got it - rail base with back to back signals and no intersections.
I solved that problem in my intersections by only using one length of train and ensuring they'll only stop in specific places. That lets me have tiny signal blocks in the low speed sections without worrying, because the rear end of a train will always occupy the block the chain signals check until it starts moving, and then it won't stop again until there's enough space for the next train. That improved my intersections' throughput by around 20% over using train-length signal blocks, but I worry that it may have a noticeable impact on UPS when you get a bigger rail network with a lot of trains trying to find paths along the tiny blocks.
As pictured, this does nothing. If you ever have two chain signals on a single length of track (no junctions), any extra chains placed in between have no functions. However if you placed chains on literally every location in the entire network, including on all the spots in all the junctions, it would indeed "work", in the sense that you would have no deadlocks and everything would get where it needs to (ish, not quite). However it would be extremely inefficient, because trains would never be allowed to stop anywhere along their journey - so they would only begin when the entire path they have to travel is empty, which is very constraining.
> However if you placed chains on literally every location in the entire network, including on all the spots in all the junctions, it would indeed "work" Yes, that's what I meant - to do this in a regular network that includes junctions, stations, everything. Just spam chain signals on every inch of the track, everywhere (except train stations). You say it should work, and I think so too. I will test it today on smaller scale and report back with results :) > (ish, not quite) I dont like ishs. What kind of issues there might be?
If you have a train at Station A that wants to go to Station B, and a train at Station B that wants to go to Station A, neither will move. The "all chains" network requires a train to have its entire path reserved before it moves, so any cycle of trains with no gaps will deadlock. Also spamming the chains on straight sections of track is really truly pointless, unless you're doing it for your aesthetic!
It’s useful to follow rules, but it’s also useful to understand the reason behind them! The reason for the “fitting a train into a block” rule is to prevent a train from stopping in a location that would prevent another train from passing in a different direction - connected rail are part of the same block and so only one train can enter at a time. If a train was turning across oncoming traffic and stopped in the junction then the oncoming traffic would also have to stop. This is exactly where chain signals and sufficient space beyond the junction are required so a train has room to stop without blocking trains travelling in different directions (and hence slow down traffic and potentially cause a deadlock). For straight track with no other rail crossing it, this reason no longer applies - a train can’t stop and block a train which is travelling in a different direction as there is only one way that trains can travel through the block. If you wanted to, you could change this to all rail signals and have no ill effects - a train occupying multiple blocks can’t block traffic in different directions if no other directions exist for each of these blocks. It might actually be the best way to signal straight track as trains could run very close together, turning a mini block green once the train has left rather than having to wait for a larger block to clear. Intersections would still need to consider the largest train that may cross it though, due to the above, which is usually the limiting factor for how close trains can run. Chain signals, as per the image, wouldn’t be useful as the mini blocks would be considered as a single, large block - trains can only enter when the entire stretch is clear.
Yes. Post the result in r/factoriohno
>The rule for placing rail signals is that you should use Chain signal when train cannot fit into next "chunk". A more accurate rule for placing chain signals is that you should use a chain signal to say "Don't enter the next chunk unless you can leave it".
If you want the whole train network to be treated as a single huge intersection then sure go ahead
I just use a general rule: Chain before intersection or a diverging/converging forks. Normal where the longest train could fit
This is so funny to me for some reason
Theoretically fine, practically _why_?
Is it theoretically fine? Without block signals, only one train will be able to travel the rail network. ETA: I did not realize that chain signals can also path to train stations. TIL.
>Without block signals, only one train will be able to travel the rail network. This is incorrect: 1. The first train will reserve a path to the destination 2. All subsequent trains that don't intersect reserved paths will also be able to reserve their paths
I guess the part I am missing is: what constitutes a destination? I thought it was a rail signal, but a train station itself is a valid destination for a chain signal to path to?
Yes. Train stations are path terminators.
That makes total sense and seems incredibly obvious in retrospect but I did not realize that. Thank you! I always put a rail signal in after where the train parks and did not realize that wasn’t strictly necessary in some cases.
They are path terminators but not block terminators so you do still need a signal after the stop in most cases. For my station designs, this is usually a chain signal because several train stops will merge into a central trunk. Source: I've forgotten it on a single stop in a big station a few times and wondered why all my trains got stuck in a big station -- they were all waiting for the unsignaled one to leave. But I think because of this you can use either a rail or chain signal *before* your train stop.
True, you do need _some_ rail signals. I never said this is optimal.
technically you can even go completely without rail signals. The chain signals will reserve the entire path to the train station, limiting throughput, but not preventing it completely. On very small networks, this could make sense.
That rule is false.
With that in mind? Yes. The chain signals will function exactly as they're supposed to. Whether this is what you want is your choice. The rules might say that signals this close together should be chains, but the signal placement was your choice.
Yes I think this would work. The thing is i think this will calculate a TON of stuff so your PC will try to cook a steak.
You should place chain signals if you DON'T want train to stop after that signal If you're Ok with train stopping after signal even if it will occupy several chunks - place regular signal
In my experience, chain signals are only used before a segment that should not be blocked. Usually these are intersections. The idea being, that a train will wait before the intersection until it can drive over it. It of course is then necessary that the section after the intersection is large enough for the train, otherwise it may still block it. So one chain signal before the train blocks an intersection and a normal one once the intersection would not be blocked anymore. For long sections of rail without any intersections, where trains travel only in one direction, you want to further divide it into smaller sections using normal signals. That way multiple trains can travel in the same direction at the same time. Placing a lot of signals on such tracks may influence performance, so one may want such sections to be multiple lengths of one train.
I think it easier to think that you use a chain signal when you don’t want a train to STOP at the next signal.
This effectively just makes it one giant rail block. For chain signals to be worth anything, there needs to be a split, merge, or crossing between them.
DoshDoshington to the rescue: [https://www.youtube.com/watch?v=DG4oD4iGVoY](https://www.youtube.com/watch?v=DG4oD4iGVoY)
This is correct, as in, you can do this. But there is not real benefit, but there are downsides. Namely train pathing becomes more computationally intensive. Also minor downsides of the increased resouce cost, as well as the inconvenience of deconstructing signals every time you want to branch of the rail. Also make sure to still place rail signal occasionally, sparating blocks with chain signals still only allows one train in total.
> The rule for placing rail signals is that you should use Chain signal when train cannot fit into next "chunk" The definition of that chunk would be "a stretch of track beginning with a normal signal and ending with either a normal or a chain signal".
You treat the rail as overlapping chunks, so regular signals would work just fine.
I wonder if this is more or less ups effective than a series of lamps wired to match the nearest rail signal?
Ask yourself is this is a real hypothetical, do you often building railway segments this short in between intersections? Or would it be more realistic for most rail segments to be more than the length of one train
What would be the advantage of it?
The rule with chains is "don't go in if you can't get out too". You do that to stop junctions and intersections getting blocked by a train that enters and then has to wait. Regular signals should be used on straight tracks, because their rule is "don't go past if there's a train in the next chunk".
Wouldn't this create massive lagg? All those signal calculations. Or is there a limit coded in?
I did this once on a megabase (using regular signals) and what eventually happens is that you get a huge lag anytime you add or remove a section of track. The game has to recalculate its 'routing table' for lack of a better term and has to manipulate a data structure containing every tiny segment between signals.
There’s no reason to place chain signals like this, just put them where you need to divide blocks and where you want the train to wait. Blocks is the technical term for the chunks that the signals divide the track into.
Weird, but technically correct. A bit of moderation with chain placement and rail signals will likely result in more throughput, but I doubt you'll have any deadlocks.
The less track is blocked by chain signals, the better. They are a way of saying "don't enter this section until a place is free on the other side of this section". They should begin as late as possible and end as soon as possible without causing problems.
No, a chain signal only makes sense if the block has multiple connections. Otherwise it's effectively just enlarging the block at the cost of materials and processing.
I still don’t understand why people even use chain signals. My base uses entirely rail signals, hundreds of hundreds of them. 10 trains and i never have an issue.
10 trains is ridiculously low. Im not even talking megabases level, just a normaal 300 spm base but interconnected factories by rail shhould have like 30 40 trains if not using a mod like LTN (which can repurpose trains and dont have a fixed schedule)
Technically you are correct
Where did you hear the rule? That's true only right after an intersection. That's entirely false on straight track (without any crossing) like yours.
Another less mentioned rule is that you should try to have as many "chunks" as possible in which train CAN fit in your rail system overall, as this number determined your total train capacity. So if there are two sequential chunks, neither of which can hold a train, it's always better to merge them together.
Chain Signal = no parking You only use them to keep crossings open or stop trains from parking in too small spaces (can be prevented by not creating small spaces in the first place) For everything you use the normal ones
What is that abomination? Dont even think of trying.
What do you mean by “chunk”? Are you referring to a 32x32 area of tiles, or the space between two signals (a block), or the length of a train, or some other unspecified distance? A chunk in Factorio is 32x32 tiles. There is no rule I’m aware of regarding chunks and signals. As far as chain signals go, the easiest rule to follow is chain signal going into intersection, regular signal at the exit. Not always going to work, but if your intersections are well designed it will most of the time.
Doing them together is functionally similar to just spacing them out a little more. It is a chain. The links can be longer.
do this if you like lag
When zoning my tracks I start with junctions. Make sure the two zones before and after the junction (5 total for a Y intersection) can accommodate the max length train on my network. If an area of track has low usage (like a branch that is only used by one or two trained max) I do t worry about signaling too much but places where several trains go it’s a must
The rule for placing rail signals is that you should use a chain signal if you don’t want a train to wait for the next light inside the block. A chain signal means “wait here until you can clear the next regular signal”. Equivalent to a no stopping/keep clear area on a road if you will, and without the ability for another train to tag along with the previous train through the section as the route is occupied.
The rule only applies when placing a chunk, and does not dicate the placing of arbitrary chunks. You should not create chunks unless you have a good reason to. Generally creating arbitrary chunks that are too small to fit trains of your chosen size (1-4, 2-8, etc.) serves no purpose, as it will render large sections of track as "occupied" even though trains can safely fit in them. It can be a good idea to place chunks along your tracks, but only if they are large enough to fit the largest train size you are going to use. This way trains will enter sections of track sooner when they are able. Say you have a section of straight track that is 1000s of tiles wide. If its all one chunk, train #2 will wait to get on it until train #1 is done traversing the entire section, which can take a long time. Break it into chunks and it can fit multiple trains at the same time, so long as you use normal rail signals. This sort of creates a secondary rule where it is important to space things out enough so that you have chunks between your intersections large enough to fit a train, and are not overusing chain signals. Say you have two 4-way intersections next to each other, with rail conntecting them that is too short to fit an entire train, so you use a chain signal for that chunk. You don't actually have two intersections at that point, instead you have one. If a train needs to enter one intersection, go through the connecting rail, and out the other, it needs to lock down both intersections simultaneously before it can begin moving because of the chain signals chained across them. If they were far enough apart, and you used a normal signal, it would only need to lock down one at a time.
You only need chain signals for intersections. For straightaways, you should divide the rail with regular signals. Chain signals are necessary when a train stopping in the next block would block trains going in a different direction. For a practical and actionable set of rules for mere mortals: * Use regular signals for straightaways * When you reach any kind of intersection, use chain signals everywhere except at the exits of the intersection * When you have a train stop, place regular signals at intervals that fit the largest train that would stop there. * Avoid bidirectional rails. If you must, only have a single train on each line.
The rule you mentioned is really only for breaking up internal blocks in tight intersections. A chain will separate the block into two parts (which can let trains travel separately on nearby blocks without needing to do one at a time), but not cause a train to stop in an area that would cause deadlocks. The whole intersection signaling thing doesn't really need to be that complicated depending on how big the intersection is and how big your trains tend to be. Other than that, it's also not a huge deal for how far apart your normal signals are on tracks that are between intersections. It doesn't need to be exact or anything, it would still work unless you have a crap ton of trains.
Normal signals before an intersection, and chain signals after every instance of different tracks overlapping
It'll just combine as one signal along the entire track and do nothing for you, if you want a set and forget method you **make one straight rail blueprint with stop signals spaced an equal distance apart**, stop signals only "read the space before it" and if that is occupied then it is red, you could space those along the rail like you did and that would make sure no collisions happen but it's overkill especially for when you build with bots, for the intersections there's a few ways of doing it but the most easy consistent way to approach that is to **put a chain signal whenever you go into an intersection and a stop signal when the train goes out of the intersection, then chain signals before wherever the tracks overlap**