3 and 4 way intersections

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Factoriointersection
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3 and 4 way intersections

Post by Factoriointersection »

If you want feedback on intersections or you think we are missing some good intersections you can post them here. I recommend that you test them on the testbench first because if you study them there you will probably find out how well they work. You can submit any type of intersection, but the OP is for now only for equally loaded 4 and 3-way intersections that allow all directions. Since the old forum topic has not been updated in four years we decided to make an updated post. It's on a shared account so that the topic won't die as the other one did.

Kano96 and HansJoachim are the creators of this new version. If you want to help, just message one of us.
Testing
Important: If you want to test your intersection in the testbench, it needs to have safe exit blocks, meaning the first block after exiting the junction has to fit an entire train. This is important to keep the results realistic, because otherwise trains could enter the intersection before they are able to exit, potentially blocking traffic or even causing a deadlock. If your intersection already has safe exit blocks included, you don't need to add them, we call this "testing with unsafe output/exits". The exit is defined as the rail signal coming after the last chain signal. Your junction can have multiple exits and each of them needs to have a safe exit block.

There is a new testing map that is more consistent and better shows intersections throughput than the old test.
Set 1 = all directions
Set 2 = straight and crossing only.
Set 3 = crossing only.
Score = ((set1+set2+set3)/3)*(2/lanes)
The practical max score is 110.
All tests are done with LLCCCC trains.
You can download the testbench and read about it Here
The goal for all intersections on here are:
- Easy to place down, (large intersections need to be divided in rotational blueprints)
- Perfectly signaling
- LHD and RHD versions
- Designed for 6 cars
Designed for multiple train lengths is a plus
If you find some errors it would be great to be notified about them.

All the test data is kept in a spreadsheet, which also has a comment linking to a python script that transform the spread sheet into forum post format.
Intersections
-- 4-Way --
-- 3-Way --
Last edited by Factoriointersection on Sat Nov 27, 2021 8:44 pm, edited 69 times in total.

Factoriointersection
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Re: 3 and 4 way intersections

Post by Factoriointersection »

Reserved

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Re: 3 and 4 way intersections [Work in progress]

Post by Tallywort »

Great to see a new intersection thread. Hope this one will be as popular as the last

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Re: 3 and 4 way intersections [Work in progress]

Post by FuryoftheStars »

Indeed, awesome to see this brought back to life!

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Re: 3 and 4 way intersections [Work in progress]

Post by aka13 »

As always, thank you for your time, great work
Pony/Furfag avatar? Opinion discarded.

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Re: 3 and 4 way intersections, Ranked by Throughput

Post by Factoriointersection »

Thanks=)
Now the post is usable.
Still work to be done though=)

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Re: 3 and 4 way intersections [Work in progress]

Post by Koub »

In the old thread, there was an additional criterium : the intersection's deadlock proneness (which I found tremendously useful). Do you plan to integrate it at some point ? Or is it out of your scope ?
Koub - Please consider English is not my native language.

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Re: 3 and 4 way intersections

Post by Factoriointersection »

Koub wrote:
Wed Nov 17, 2021 5:19 pm
In the old thread, there was an additional criterium : the intersection's deadlock proneness (which I found tremendously useful). Do you plan to integrate it at some point ? Or is it out of your scope ?
After the 0.15.27 update intersections will either deadlock in normal traffic or it will not. So the old deadlock rating is useless. For posted intersections that deadlock we'll comment it:)
aaargha wrote: With the changes made to the path-finding algorithm in 0.15.27 almost all intersections rated from B to E (inclusive) are safe as long as the player does neither, disable the train station the train is heading to while travelling, nor, destroy/build rails/signals that makes the train's path invalid.

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Re: 3 and 4 way intersections

Post by Koub »

Haha I feel stupid. I confess I have almost never used trains, I guess the last time was before 0.15.27. Time sure does fly.
Koub - Please consider English is not my native language.

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Re: 3 and 4 way intersections

Post by hansjoachim »

Koub wrote:
Wed Nov 17, 2021 8:04 pm
Haha I feel stupid. I confess I have almost never used trains, I guess the last time was before 0.15.27. Time sure does fly.
it does=)

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Re: 3 and 4 way intersections

Post by farcast »

After looking at junctions for a while, especially the multicross junction, I thought of seeing what would happen if I just spaced out that triple crossing you see in a lot of T-junctions. This "Double Image" junction is the result.
Double Image
RHD Scores
Set 1: 53
Set 2: 59*

You can improve the set 1 score to 57 by breaking the exit block into a 2 car block and a 4-5 car block after it. If you do this, then there needs to be another 6 car block afterwards, as well as only using 5-6 car trains, to prevent deadlocks. I chose to list the score for the more general use case.

* The set 2 score is heavily dependent on two things. The signal spacing leading up to the junction needs to match the length of an inner buffer, and the three inner buffers need to be near exactly the same size. When these two conditions are met, then crossings will synchronize in an extremely satisfying way. My efforts to disrupt the timing revealed this behavior to be stable, meaning crossings will naturally synchronize like this. If either condition isn't met, then this behavior will be unstable, crossings won't synchronize, and set 2 performance will drop to 43.
Synchronized crossing.gif
Synchronized crossing.gif (164.77 KiB) Viewed 3700 times
Extending the buffers to fit 2 trains only improved set 1 TPM from 53 to 57, and had no effect on set 2 TPM, so I decided not to include that since splitting the exit block could get the same benefit, though I haven't tested using both.

Using oversized 1 train buffers increased the set 1 score to 55, but crossing behavior became unstable. I tested again after increasing the signal spacing from 6 cars to matching the inner buffer length, and crossing behavior became stable again. The set 2 score after increasing the signal spacing was 63 TPM while the set 1 score dropped back to 53. At this point I realized ~63 TPM might be the hard limit for crossing performance without using multiple parallel crossing lanes for each entrance, as there was never not a train passing the chain signals at near full speed.

Bonus RHD Double Double Image scores (without split exits)
Set 1: 54
Set 2: 55
Set 3: 74

Blueprints are for 6 car trains and 7 car 27 rail tile signal spacing, but would also work with 6 car signal spacing. After figuring out that I can switch between set 1 and set 2 without waiting for trains to clear out, I found out that the tolerance for self synchronization is even less than I thought. Signal spacing really needs to be near exactly the same as the buffer length. I think it might actually be buffer length + chain signal blocks, but in this case there's not much difference.

Last edited by farcast on Sat Nov 20, 2021 8:12 am, edited 1 time in total.
Efficient inefficient design.

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Re: 3 and 4 way intersections

Post by mrvn »

Wouldn't it be better to have 4 lanes between the 2 Ts?

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Re: 3 and 4 way intersections

Post by farcast »

mrvn wrote:
Sat Nov 20, 2021 3:41 am
Wouldn't it be better to have 4 lanes between the 2 Ts?
Good idea! I was going for minimal buffers, but since buffers need to be there anyway, I might as well make good use of the space.
Double Double Image v2
New RHD scores
Set 1: 62
Set 2: 56
Set 3: 77

Maybe there's a better way to do it, but it's hard to make changes without making crossings unstable. I get the feeling this concept doesn't scale very easily, if at all.

Efficient inefficient design.

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Re: 3 and 4 way intersections

Post by Kano96 »

Hey, nice intersection! The synchronized crossings are mesmerizing.
Do you want to have it added to the post? If yes, which version? V2 obviously performs better, but I also like the simplicity of the original.

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Re: 3 and 4 way intersections

Post by mmmPI »

very inspiring :)

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Re: 3 and 4 way intersections

Post by farcast »

Kano96 wrote:
Sat Nov 20, 2021 7:34 pm
Hey, nice intersection! The synchronized crossings are mesmerizing.
Do you want to have it added to the post? If yes, which version? V2 obviously performs better, but I also like the simplicity of the original.
I would love for it to be added, thanks! I think v2 should be used, since it allows for simultaneous left & right turns from one T to the next, which is situationally better. It still has synchronized crossings, so it's just better all around.
Efficient inefficient design.

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Re: 3 and 4 way intersections

Post by DaveMcW »

Branch Predictor

4-Way, 2 Lane, Unbuffered.

Image



This intersection attempts to keep a pair of compatible lanes running at high speed as long as possible. It works best when many trains in a row are going to the same destination.

The main intersection is 58x58, but the train detector requires the 7-tile-spaced signals to extend past the end of the first train. So the blueprint for 6 wagon trains is 114x114. There is probably room to optimize these numbers by adjusting the train detector.

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Re: 3 and 4 way intersections

Post by Factoriointersection »

DaveMcW wrote:
Sun Nov 21, 2021 7:04 am
Branch Predictor

4-Way, 2 Lane, Unbuffered.

Image



This intersection attempts to keep a pair of compatible lanes running at high speed as long as possible. It works best when many trains in a row are going to the same destination.

The main intersection is 58x58, but the train detector requires the 7-tile-spaced signals to extend past the end of the first train. So the blueprint for 6 wagon trains is 114x114. There is probably room to optimize these numbers by adjusting the train detector.
That is pretty cool:) it gets a score of 53 which is better than an 2 lane unbuffered intersections. Regulary turning signals of, with combinators, causes trains to repath and try to avoid the intersection.

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Re: 3 and 4 way intersections

Post by Lubricus »

I have an design that I haven't seen any other use and shuldn't be to bad. 4-way unbufferd
https://factorioblueprints.tech/api/str ... c6df053472

https://factorioblueprints.tech/bluepri ... 450d3521dd

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Re: 3 and 4 way intersections

Post by causa-sui »

2-lane, 4-way buffered by Tallinu. RHD.



Results in testbench 4.2.1, factorio 1.1.46 (build 59110, linux amd64): 45/48/45/46

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