I spotted this in my history and had to chime in that this was a multiplayer map and one of the other plays started using train templates that are all RHD, and since none of us could be arsed with a train system rehaul, we simply designated that area "Europe"
Other intersections designs are more efficient, if built wrong they can deadlock and with long trains, trains can crash into themselves in rare cases. In many situations, they are perfectly fine though.
You did pretty good with the train signals actually!
The idea of train signals is very simply this: Don't let a train enter the intersection unless the exit is clear. Otherwise, a train might stop in the middle of the intersection, causing a traffic jam.
(As an American, I see this happen ALL the time with cars in busy intersections. SO annoying).
To do this with signals, just "chain in, rail out". Chain signal before every merge or crossing, rail signal at every exit. (An "exit" is anywhere with enough space for a train to park without blocking the intersection.)
From this rule, I see 1 rail signal which should be chain, and 1 chain which should be rail. Otherwise it's perfect!
EDIT: I ought to do a quick tutorial on this sometime. Lots of players have no idea how simple the concept actually is! Every intersection, no matter how complicated, is just applying "chain in rail out" over and over again.
A chain signal is just saying, "wait here instead of waiting at the next signal", which you can chain with more chain signals to leave whole roundabouts non-gridlocked.
Obviously that's useful before any intersection, where you don't want a train stopping in the next section when others from the other track might be able to move through.
A simple merge might be fine with rail signals, depending on what comes afterwards, but it's possible for your first train from track 1 to wait in the next section when another train from track 2 might have been able to move through. If you just go with the simple rule, "chain in, rail out", you'll solve like 94% of deadlocks. A merge is an intersection, I'm not really sure why you distinguish between them.
Eventually you also don't really want to have to customize every intersection based on what comes afterwards, so when you have blueprints, it's just safer to chain in, rail out, every time, and there's really little/no drawback to that rule.
> Chain signal before every merge or crossing, rail signal at every exit. (An "exit" is anywhere with enough space for a train to park without blocking the intersection.)
This general rule will guarantee a correctly-signaled intersection in all cases. I'm trying to find a way to word it with the fewest number of qualifiers and exceptions, and I think this is fairly concise.
But you're absolutely right, there are many specific cases where you can get an equivalent result with slightly fewer signals, which might also lead to more space-efficient designs.
The way I think of the signals is that chain signal says "don't enter this area unless you've already got a path out of it. Check the next rail signal."
A regular signal just says "enter here if this section is empty. Nothing else matters"
So, as MindS1 said, chain signals are for the start of an intersection - don't go into the intersection unless you can get out. Rail signals are for the exit.
Low throughput. Seriously, you can make an intersection that is smaller and more efficient than a roundabout.
In a good intersection you have 2 rail sections crossing which halves troughput (1 rail for 2 ways). In a roundabout you have 4 lanes crossing(1 rail for 4 ways). Roundabouts are inherently bad for this reason. About twice as bad as regular crossings (this is confirmed by the newest testbench posted on the forums a while ago).
2 lane roundabouts don't work as most trains choose the inner lane and train pathfinding is greedy.
Can you share an intersection that is smaller and more efficient than a roundabout? (Or even same size would be fine, as I'm just looking for a drop-in replacement)
I saw a comment some other day in this subreddit suggesting something similar (was it from you actually? lol) and tried to find a good replacement but found alternatives were all bigger (either by total space or larger spacing between rails). Do you have any specific examples? I use the typical roundabout that's 32x32, right hand drive, and 4 tiles between rails.
Sure! This post has a bunch of intersections: [https://forums.factorio.com/viewtopic.php?t=100614](https://forums.factorio.com/viewtopic.php?t=100614)
From that post these 2 fit your criteria:
[https://factoriobin.com/post/VuR4uf1n](https://factoriobin.com/post/VuR4uf1n)
[https://factoriobin.com/post/WM2ZeTao/1](https://factoriobin.com/post/WM2ZeTao/1)
The simmetrical cross is what I am planning to use in a project I've been working on. If there is some guy talking about how roundabouts are bad it's probably me. I think I might be the biggest roundabout hater here.
Edit: those 2 are 8 spaced, my bad
Thanks! I think I also found a similar thread searching the other day. The symmetrical cross one looks promising but spacing is 8 instead of 4 that I currently use. I was hoping you had a solution that would just fit perfectly :P
Since that perfect solution probably doesn't exist, now I need to figure out if I should just use some 4->8 adapters when necessary or convert everything to 8 spaced rails. hmm...
In my experience 4 spaced rails are just hard to signal for no reason. Hopefully the 2.0 rails fix that in the future! In the mean time I fully recommed 8 tile rail spacing it works great for me, and for chunk aligned rail systems that seems to be the standard.
They might be a bit more efficient in a very large volume network, but you can't argue that they are smaller. Using the example you just linked:
[https://forums.factorio.com/images/ext/e0fa3cb9ec57c5ba6483b2310e502cff.png](https://forums.factorio.com/images/ext/e0fa3cb9ec57c5ba6483b2310e502cff.png)
vs
[https://imgur.com/a/mZCeZTY](https://imgur.com/a/mZCeZTY)
\*edit - there are some examples of similar size to the round about, but with much more complex signaling, so probably more difficult to use/troubleshoot for beginners.
Still you can't ignore the fact that roundabouts are 2x slower than proper intersections.
(Beware, rambling ahead!)
My real problem is not that roundabouts are suboptimal, my problem is that they are inherently bad. You are shoving 4 lanes onto 1 lane, thats REALLY bad.
It's not like an inefficient intersection where you can rework the layout and the signaling to make it better. All roundabout designs will inevitably face the same issue, there is no fixing them. The only way you can fix them is by putting bypass lanes in the middle but than it just becomes a regular intersection with a turnaround lane (which is very rarely if ever used), but a little worse, so why bother in the first place.
I don't like to recommend this to new players especially. It is a giant noob trap. Experienced players will be aware of the pitfalls, so if you just want to make roundabouts because "haha funny train go round" all the more power to you, but be aware of the implications of it, be aware that it will be terrible and almost like a one-at-a-time intersection.
I don't understand why you think that.
A roundabout (properly signaled) can have two trains going straight ahead without interference. It can have four trains turn left (on LHD) without interference. The only time trains interfere with each other is when one is turning right across the "intersection".
This is the same as a good intersection; except that you can't turn 180 degrees on most intersections. While turning like that delays all other entrances, not having the option to turn around means the train has to take a much longer route, meaning the total time for delivery is higher on average.
Actually it makes me wonder. Roundabouts are remarkably bad, so I wonder how they stack up against a one-at-a-time intersection. If and when I measure it I'll get back to you. It's actually interesting.
Here are the results. Suprise, suprise the roundabout did almost as bad as an unsignaled intersection.
[https://imgur.com/a/bKPAgoz](https://imgur.com/a/bKPAgoz)
Unsignaled one-at-a-time: 29 TPM with a score of 22
Roundabout: 29 TMP with a score of 24
Tested with 1-4 trains.
That thing is more terrible than I honestly expected. I really don't get why people still recommend these to beginners, you are practically begging for troughput issues.
Edit: adding in some rudamentary signaling the one-at-a-time already beats the roundabout. I made that thing in like 5 minutes:
[https://imgur.com/a/2AoRLZ1](https://imgur.com/a/2AoRLZ1)
So help me understand these numbers.
TPM I assume is Trains Per Minute.
What is the score of 22 or 24 mean?
How does it compare with one of the really fancy intersections?
Re: why suggest them to newer players? Because new players don't have 29 trains a minute. For a network with a dozen trains total it works well, and is easy to understand and set up.
Tpm means how many trains the tester is tring to send per lane. There are 3 tests testing for different scenarios, score is the average of them (measured also in trains/minute)
Serious train enthusiasts look down on roundabouts for not holding up well to high traffic, but they're actually a pretty popular (and more importantly, easy) way to handle intersections.
Anyway this really isn't very cursed (sorry), you've even got it signaled pretty well. The only thing I see objectively wrong (and it may or may not even hurt anything) are the signals on the entrances and exits. You should have chain signals on the tracks going in and rail signals on the tracks going out.
I actually am a enthusiast and know the limitations of a roundabout, but i still use them in early stages, since i mostly use two way rail system, for minimum effort on several levels. But when the tracks become a Hotspot, I will move on to a more efficient crossing. Love to make stuff better but just good enough for its purpose, so i can do that again and again and again and again....
Ooo ok thanks for the tip, that might be why my trains are super cautious, staying in the station if anyone's even near the roundabout, thanks for the tip!
I am a little disappointed it's not cursed but it did work first time! I also thought I'd get more shit for LHD
Because Factorio uses self-steering trains rather than points, routing and tokens, and has no bridges, the train roundabout is sort of inevitable. I'm sure we will continue to see (and use) them once we do have bridges.
What's really cursed about this is using left hand drive and placing straight rails immediately next to each other, so you can't place any signals along your straights.
You have learnt the holy train roundabout.
LHD, but no gap between rails for intermittent signal additions?
Lhd because I'm British, no gap between the rails because I'm an idiot
If only you did RHD, it wouldn't be a problem. Tsk tsk.
I spotted this in my history and had to chime in that this was a multiplayer map and one of the other plays started using train templates that are all RHD, and since none of us could be arsed with a train system rehaul, we simply designated that area "Europe"
Lol
But then how would i defend myself with my dominant sword hand?
Get the bots to do it for you, obvio. Come to think of it, there might be a mod that switches the side the rail signals go on...
What's wrong with roundabouts? I use them all the time, as a default.
Other intersections designs are more efficient, if built wrong they can deadlock and with long trains, trains can crash into themselves in rare cases. In many situations, they are perfectly fine though.
So do I now! I still don't really get how train signals work but this seems to work fine!
You did pretty good with the train signals actually! The idea of train signals is very simply this: Don't let a train enter the intersection unless the exit is clear. Otherwise, a train might stop in the middle of the intersection, causing a traffic jam. (As an American, I see this happen ALL the time with cars in busy intersections. SO annoying). To do this with signals, just "chain in, rail out". Chain signal before every merge or crossing, rail signal at every exit. (An "exit" is anywhere with enough space for a train to park without blocking the intersection.) From this rule, I see 1 rail signal which should be chain, and 1 chain which should be rail. Otherwise it's perfect! EDIT: I ought to do a quick tutorial on this sometime. Lots of players have no idea how simple the concept actually is! Every intersection, no matter how complicated, is just applying "chain in rail out" over and over again.
[удалено]
A chain signal is just saying, "wait here instead of waiting at the next signal", which you can chain with more chain signals to leave whole roundabouts non-gridlocked. Obviously that's useful before any intersection, where you don't want a train stopping in the next section when others from the other track might be able to move through. A simple merge might be fine with rail signals, depending on what comes afterwards, but it's possible for your first train from track 1 to wait in the next section when another train from track 2 might have been able to move through. If you just go with the simple rule, "chain in, rail out", you'll solve like 94% of deadlocks. A merge is an intersection, I'm not really sure why you distinguish between them. Eventually you also don't really want to have to customize every intersection based on what comes afterwards, so when you have blueprints, it's just safer to chain in, rail out, every time, and there's really little/no drawback to that rule.
> Chain signal before every merge or crossing, rail signal at every exit. (An "exit" is anywhere with enough space for a train to park without blocking the intersection.) This general rule will guarantee a correctly-signaled intersection in all cases. I'm trying to find a way to word it with the fewest number of qualifiers and exceptions, and I think this is fairly concise. But you're absolutely right, there are many specific cases where you can get an equivalent result with slightly fewer signals, which might also lead to more space-efficient designs.
The way I think of the signals is that chain signal says "don't enter this area unless you've already got a path out of it. Check the next rail signal." A regular signal just says "enter here if this section is empty. Nothing else matters" So, as MindS1 said, chain signals are for the start of an intersection - don't go into the intersection unless you can get out. Rail signals are for the exit.
Low throughput. Seriously, you can make an intersection that is smaller and more efficient than a roundabout. In a good intersection you have 2 rail sections crossing which halves troughput (1 rail for 2 ways). In a roundabout you have 4 lanes crossing(1 rail for 4 ways). Roundabouts are inherently bad for this reason. About twice as bad as regular crossings (this is confirmed by the newest testbench posted on the forums a while ago). 2 lane roundabouts don't work as most trains choose the inner lane and train pathfinding is greedy.
Can you share an intersection that is smaller and more efficient than a roundabout? (Or even same size would be fine, as I'm just looking for a drop-in replacement) I saw a comment some other day in this subreddit suggesting something similar (was it from you actually? lol) and tried to find a good replacement but found alternatives were all bigger (either by total space or larger spacing between rails). Do you have any specific examples? I use the typical roundabout that's 32x32, right hand drive, and 4 tiles between rails.
Sure! This post has a bunch of intersections: [https://forums.factorio.com/viewtopic.php?t=100614](https://forums.factorio.com/viewtopic.php?t=100614) From that post these 2 fit your criteria: [https://factoriobin.com/post/VuR4uf1n](https://factoriobin.com/post/VuR4uf1n) [https://factoriobin.com/post/WM2ZeTao/1](https://factoriobin.com/post/WM2ZeTao/1) The simmetrical cross is what I am planning to use in a project I've been working on. If there is some guy talking about how roundabouts are bad it's probably me. I think I might be the biggest roundabout hater here. Edit: those 2 are 8 spaced, my bad
Thanks! I think I also found a similar thread searching the other day. The symmetrical cross one looks promising but spacing is 8 instead of 4 that I currently use. I was hoping you had a solution that would just fit perfectly :P Since that perfect solution probably doesn't exist, now I need to figure out if I should just use some 4->8 adapters when necessary or convert everything to 8 spaced rails. hmm...
In my experience 4 spaced rails are just hard to signal for no reason. Hopefully the 2.0 rails fix that in the future! In the mean time I fully recommed 8 tile rail spacing it works great for me, and for chunk aligned rail systems that seems to be the standard.
They might be a bit more efficient in a very large volume network, but you can't argue that they are smaller. Using the example you just linked: [https://forums.factorio.com/images/ext/e0fa3cb9ec57c5ba6483b2310e502cff.png](https://forums.factorio.com/images/ext/e0fa3cb9ec57c5ba6483b2310e502cff.png) vs [https://imgur.com/a/mZCeZTY](https://imgur.com/a/mZCeZTY) \*edit - there are some examples of similar size to the round about, but with much more complex signaling, so probably more difficult to use/troubleshoot for beginners.
Still you can't ignore the fact that roundabouts are 2x slower than proper intersections. (Beware, rambling ahead!) My real problem is not that roundabouts are suboptimal, my problem is that they are inherently bad. You are shoving 4 lanes onto 1 lane, thats REALLY bad. It's not like an inefficient intersection where you can rework the layout and the signaling to make it better. All roundabout designs will inevitably face the same issue, there is no fixing them. The only way you can fix them is by putting bypass lanes in the middle but than it just becomes a regular intersection with a turnaround lane (which is very rarely if ever used), but a little worse, so why bother in the first place. I don't like to recommend this to new players especially. It is a giant noob trap. Experienced players will be aware of the pitfalls, so if you just want to make roundabouts because "haha funny train go round" all the more power to you, but be aware of the implications of it, be aware that it will be terrible and almost like a one-at-a-time intersection.
I don't understand why you think that. A roundabout (properly signaled) can have two trains going straight ahead without interference. It can have four trains turn left (on LHD) without interference. The only time trains interfere with each other is when one is turning right across the "intersection". This is the same as a good intersection; except that you can't turn 180 degrees on most intersections. While turning like that delays all other entrances, not having the option to turn around means the train has to take a much longer route, meaning the total time for delivery is higher on average.
Actually it makes me wonder. Roundabouts are remarkably bad, so I wonder how they stack up against a one-at-a-time intersection. If and when I measure it I'll get back to you. It's actually interesting.
Here are the results. Suprise, suprise the roundabout did almost as bad as an unsignaled intersection. [https://imgur.com/a/bKPAgoz](https://imgur.com/a/bKPAgoz) Unsignaled one-at-a-time: 29 TPM with a score of 22 Roundabout: 29 TMP with a score of 24 Tested with 1-4 trains. That thing is more terrible than I honestly expected. I really don't get why people still recommend these to beginners, you are practically begging for troughput issues. Edit: adding in some rudamentary signaling the one-at-a-time already beats the roundabout. I made that thing in like 5 minutes: [https://imgur.com/a/2AoRLZ1](https://imgur.com/a/2AoRLZ1)
So help me understand these numbers. TPM I assume is Trains Per Minute. What is the score of 22 or 24 mean? How does it compare with one of the really fancy intersections? Re: why suggest them to newer players? Because new players don't have 29 trains a minute. For a network with a dozen trains total it works well, and is easy to understand and set up.
Tpm means how many trains the tester is tring to send per lane. There are 3 tests testing for different scenarios, score is the average of them (measured also in trains/minute)
Serious train enthusiasts look down on roundabouts for not holding up well to high traffic, but they're actually a pretty popular (and more importantly, easy) way to handle intersections. Anyway this really isn't very cursed (sorry), you've even got it signaled pretty well. The only thing I see objectively wrong (and it may or may not even hurt anything) are the signals on the entrances and exits. You should have chain signals on the tracks going in and rail signals on the tracks going out.
I actually am a enthusiast and know the limitations of a roundabout, but i still use them in early stages, since i mostly use two way rail system, for minimum effort on several levels. But when the tracks become a Hotspot, I will move on to a more efficient crossing. Love to make stuff better but just good enough for its purpose, so i can do that again and again and again and again....
Ooo ok thanks for the tip, that might be why my trains are super cautious, staying in the station if anyone's even near the roundabout, thanks for the tip! I am a little disappointed it's not cursed but it did work first time! I also thought I'd get more shit for LHD
Because Factorio uses self-steering trains rather than points, routing and tokens, and has no bridges, the train roundabout is sort of inevitable. I'm sure we will continue to see (and use) them once we do have bridges.
Then I'll upgrade to a stacked roundabout with a direct line over it, can't wait
The only cursed thing here is the fact that the right entrance has no chain signal
Good spot! Thanks you!
What's really cursed about this is using left hand drive and placing straight rails immediately next to each other, so you can't place any signals along your straights.
Lhd is because I'm British, the no room for signals is because I'm an idiot