Help solving bottleneck

[One33Seven]

So I've got myself rather efficient processing and transport systems. There is just one bottleneck in the whole system and that is the exit of my unload train station.

Station

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So trains will come in from the right, there's a huge buffer area in front of the station. The will go into the station, unload and then exit from the left. The problem is that only 2 trains can exit at once, one going down and another going up.

i would like to increase the throughput of trains in this area but I'm not sure how to achieve this. I'm even not sure if this is possible at all because I'm thinking this is systemic to my design.

So any hints, tips and idea on how-to improve this area would be appreciated.

I've taken into account that I would probably have to expand this station at some point so there's a vast area of empty space around the station.

area

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[Engimage]

Take a look at several my advices in this thread
viewtopic.php?f=18&t=49636
Can't write more from mobile
Anyways I would strongly encourage you to avoid 2-way movement on exit line. You can split train station into bottom group all exiting south and top group all exiting north but never let them go on collision courses as you have to make all exit line a single block in this case which will dramatically bottleneck output

[One33Seven]

Ah yes, I've thought about replacing the chain signals with regular signals but didn;t have an idea what the effect of this would be (fearing deadlocks). What you are saying is that it WON'T cause deadlocks? Also your merge only goes into 1 direction, my merge can go into 2 directions. I will experiment with this in a separate save game.

[Greybeard_LXI]

PacifyerGrey linked to a good thread on this.

One thing that would help, if you want trains to exit both north and south, is to make the exit two one way tracks instead of one two way track. Your north bound would still be slower but south bound should go a bit quicker.

I suspect that if you get the trains moving you will find a bottleneck at the entrance, on the right.

[BlakeMW]

Having exit buffers able to hold 1 train is highly useful, also it looks like you only use 1 lane for both directions which doesn't seem optimal: you'd be better off having a separate north and south rail and perform more complicated merges from the exits - the inner lane will get blocked a lot by trains crossing it, but it'd still be an improvement. Also if you don't mind getting down and dirty with circuit network conditions you can prevent trains merging into the outer lane when there is an oncoming train, which would allow a train which enters the exit lane to quickly accelerate to freedom. Another circuit solution is batching (traffic lights): you wire up the signals to alternatively let all the northbound trains go, then let all the southbound trains go, that way you don't get trains blocked by other trains crossing the tracks.

Generally though it is just a bad idea to concentrate too many trains in one area, there are only bandaid fixes - the kind of thing where you put a lot of work into getting +25% throughput. In the long run you are better served by exploiting compression, for example instead of shipping copper ore to your factory, make electronic circuits at an output, since each EC is worth 2.5 plates and they stack 4x deeper, meaning 1 EC train can replace 6 copper ore and 4 iron ore trains. It's hard to get a 10x improvement in throughput out of even the most fancy and optimized exit merges.

[Engimage]

Ah yes, I've thought about replacing the chain signals with regular signals but didn;t have an idea what the effect of this would be (fearing deadlocks). What you are saying is that it WON'T cause deadlocks? Also your merge only goes into 1 direction, my merge can go into 2 directions. I will experiment with this in a separate save game.

Read carefully what I wrote. You should NOT make exit two way. You should separate stations into two groups with south half all exiting southwards and northern group all exiting northwards. Do not make mixed exits as those WILL deadlock as well as they will limit throughput. Merge will work much faster if trains follow each other as they will be able to share the exit lane

[One33Seven]

Ah yes, I've thought about replacing the chain signals with regular signals but didn;t have an idea what the effect of this would be (fearing deadlocks). What you are saying is that it WON'T cause deadlocks? Also your merge only goes into 1 direction, my merge can go into 2 directions. I will experiment with this in a separate save game.

Read carefully what I wrote. You should NOT make exit two way. You should separate stations into two groups with south half all exiting southwards and northern group all exiting northwards. Do not make mixed exits as those WILL deadlock as well as they will limit throughput. Merge will work much faster if trains follow each other as they will be able to share the exit lane

Ah, could've sworn your post ended at the sentence: "Can't write more from mobile". Did you edit it by chance?

Anyway splitting into two groups isn't viable for because I have mines all over the place. both up and down. All that would do is force some trains to route around the station to go north and I fear this would cause traffic jams somewhere else.

[Engimage]

Trust me letting output merge lane be two way single block is so much worse than adding a spare detour around your station for such trains...
The main problem here is the merge. When trains do line up one after another they tend to jam much less. Just provide quality merges and non deadlockable intersections (preferably not roundabouts like you do) around station with probably 4 lane rails for main bus and you are fine

[BlakeMW]

Just start with the low hanging fruit, the two-way track like this:

two way.jpg (238.23 KiB) Viewed 5255 times

This allows multiple trains to depart simultaneously and should probably at least double exit throughput. Note there is no need for chain signals at exits like this. It's a little tough to explain why, but basically trains can always "drain out" from either side and as the trains leave other trains will be un-blocked.

[Engimage]

Just start with the low hanging fruit, the two-way track like this:

two way.jpg

This allows multiple trains to depart simultaneously and should probably at least double exit throughput. Note there is no need for chain signals at exits like this. It's a little tough to explain why, but basically trains can always "drain out" from either side and as the trains leave other trains will be un-blocked.

This solution is much better than initial single lane setup
However chain signals here would actually be nice right on station exit (others staying normal) as trains turning left might block trains on exit lane moving right for prolonged time with absolutely no need. If a turn right would be more smooth there would be a space to fit that signal directly before turn left (without it effecting turn right) for more optimal logic
These chain signals are not required as this design won't deadlock but will add some more throughput

[One33Seven]

So what I did first is split the north and south exits into two seperate tracks and put in regular signals instead of chained signals. Took me a while to figure out a working design but this is the end result.

design

bottleneck1.png (964.37 KiB) Viewed 5240 times

What happens now is that the trains going north and south are blocking each other on the intersections infront of the stations. Also the bottleneck is now moved towards the roundabouts north and south of the exits, this yet again strengthens my belief this is systematic to this design.

replace

bottleneck.png (45.7 KiB) Viewed 5240 times

Trust me letting output merge lane be two way single block is so much worse than adding a spare detour around your station for such trains...
The main problem here is the merge. When trains do line up one after another they tend to jam much less. Just provide quality merges and non deadlockable intersections (preferably not roundabouts like you do) around station with probably 4 lane rails for main bus and you are fine

What I'm going todo next is try @PacifyerGrey suggestion to split the exits right in half, think that is the most sane short term solution. Long term I'm going to design a bufferzone north and south of the station so trains can flow into the network without stopping.

Currently I've put the chained signals back in on the two exit design, just to prevent the whole spaghetti mess of trains.

[BlakeMW]

However chain signals here would actually be nice right on station exit (others staying normal) as trains turning left might block trains on exit lane moving right for prolonged time with absolutely no need. If a turn right would be more smooth there would be a space to fit that signal directly before turn left (without it effecting turn right) for more optimal logic
These chain signals are not required as this design won't deadlock but will add some more throughput

Yeah , tho it's almost invisible I actually did place chain signals at the stations. I'm not entirely convinced it helps in and of itself though... the trains on the top track don't have to wait for much and clear out pretty quickly (and this can be improved even more by adding additional lanes) so a train which is turning left won't be waiting for long - if at all.
In this kind of case I believe optimal train control involves using circuit network to act predictively - a simple chain signal means "you can't leave because a block you want to go through is currently occupied" even though this may not be true by the time the train has reached that block. With circuit network to forward red signals this can be refined to "you can't leave because a block you want to go through will be occupied by the time you get there".

What happens now is that the trains going north and south are blocking each other on the intersections infront of the stations. Also the bottleneck is now moved towards the roundabouts north and south of the exits, this yet again strengthens my belief this is systematic to this design.

Yeah that's the thing, track can only handle so many trains before it gets bogged down. Adding dedicated turning lanes can help a lot, then those dedicated turning lanes tend to turn into outright 4 lane track - but 4 lanes inevitably means more track crossings so doesn't provide double the throughput. As I said in my original post exploiting compression is an order of magnitude more effective than optimizing station/junction designs (altough it is terribly fun to optimize stations and junctions).

[One33Seven]

I did some testing, leaving the game running and trying to judge the throughput.

I split the exits in two, 8 stations going north and 7 stations going south. As I suspected this shifted the stress onto the two roundabouts north and south from the stations. This finally confirms my original thoughts that this is systemic and I need to design something else. Next weekend I'm going to put some time and thought into designing some kind of bufferzone.

[aaargha]

I did some testing, leaving the game running and trying to judge the throughput.

I split the exits in two, 8 stations going north and 7 stations going south. As I suspected this shifted the stress onto the two roundabouts north and south from the stations. This finally confirms my original thoughts that this is systemic and I need to design something else. Next weekend I'm going to put some time and thought into designing some kind of bufferzone.

I'd recommend moving away from the roundabouts as well, they're going to be a bottleneck almost no matter what you do. Take a look here for some alternatives, there are many that are better with regards to throughput and/or deadlocks (seeing the problems you're having in the other thread).

[One33Seven]

I'd recommend moving away from the roundabouts as well, they're going to be a bottleneck almost no matter what you do. Take a look here for some alternatives, there are many that are better with regards to throughput and/or deadlocks (seeing the problems you're having in the other thread).

Yes thanks, I've seen those but I don't like to take ready made designs. For me the whole point of the "game" is to look at a problem, analyze it and come up with solutions. Currently I came up with something which is similar to the "2-lane compact" in that list, mainly because my layout requires a big electrical pole (isn't that a mast?) to be at the middle of an intersection because power distribution to outposts goes parallel to train tracks.

I think the only way I can solve this is to upgrade from a 2 track to a 4 track design but that would require me to mine away some resources which are scattered around the base and also fill in a few lakes. This is going to take a long long looooon time.

[aaargha]

Yes thanks, I've seen those but I don't like to take ready made designs. For me the whole point of the "game" is to look at a problem, analyze it and come up with solutions. Currently I came up with something which is similar to the "2-lane compact" in that list, mainly because my layout requires a big electrical pole (isn't that a mast?) to be at the middle of an intersection because power distribution to outposts goes parallel to train tracks.

I think the only way I can solve this is to upgrade from a 2 track to a 4 track design but that would require me to mine away some resources which are scattered around the base and also fill in a few lakes. This is going to take a long long looooon time.

That's the spirit!

If you want me to test/look at/discuss any design just say the word, I should be able to do so for at least the next few days before I'm heading out of town. If you want to see what kind of throughput your designs achieve with your train/fuel setup, or you just want to do some quick tests yourself, the setup I'm using is linked in my signature.

Also, if you've not tried running your trains on rocket fuel, try that, it'll probably help a lot. Then again, as you're running only one loco I'm guessing you're already on rocket fuel.

Anyway, good luck!