Trains and optimal layouts

[xBlizzDevious]

Hi all,

I've always built my trains with roundabouts as that's the way that makes sense in my head, but I've seen very few Youtubers use any loops - in fact, they're all strongly against it... Especially so in mega-bases which is what I'm beginning a build of in my current save.

For that reason, I've decided to try a four-lane track with double-headed trains. The way I've planned for the junctions to work is that all trains leaving at a junction will have to be on the closest lane to their exit, rather than having all lanes feeding to and from every junction. I have lane switchers feeding into the correct lane just before any junction and ones feeding back to the "fast lane" just after. I will also set up lane switchers periodically along the track to allow trains to overtake others if they're slowing for junctions and so on. Is this a good idea or a bad idea? Is it more effective to just have all junctions feed to and from all lanes?



Here is a picture of a junction I've just built using the above idea - driving on the left. Is this signalled correctly?

Main line to minor line - junction example.

Factorio 2016-05-05 05-25-07-558.png (8.96 MiB) Viewed 29852 times

[SyncViews]

The problem I see there is that with Factorio's lack of path signalling (see OpenTTD), that in several places 2 parallel lines are in a single signal block, and in the middle 3 of 4 lines are, plus both junction lines (so 5/6 total). This means that if you have trains running next to each other (say the bottom 2 lines of the 4-way), or in opposite directions, that in many cases those trains will needlessly block each other. This may be OK if you have few junctions, and lower traffic, but effectively at high traffic levels you limit through put to be worse than just 2 lines.

Having signals between the lines (with chain signals to help prevent trains stopping across the junction) can make the parallel tracks be separate signal blocks.

Then the major goal would be with routing to reduce the number of trains that need to cross all 4 tracks. One option I have been playing with is to actually run my 4-ways in pairs, e.g. for a east-west track like yours, top to bottom, E-W-E-W, rather than E-E-W-W, and then have the junction just on the bottom pair, with the top lines entirely bypass it.

[xBlizzDevious]

The problem I see there is that with Factorio's lack of path signalling (see OpenTTD), that in several places 2 parallel lines are in a single signal block, and in the middle 3 of 4 lines are, plus both junction lines (so 5/6 total). This means that if you have trains running next to each other (say the bottom 2 lines of the 4-way), or in opposite directions, that in many cases those trains will needlessly block each other. This may be OK if you have few junctions, and lower traffic, but effectively at high traffic levels you limit through put to be worse than just 2 lines.

Having signals between the lines (with chain signals to help prevent trains stopping across the junction) can make the parallel tracks be separate signal blocks.

Then the major goal would be with routing to reduce the number of trains that need to cross all 4 tracks. One option I have been playing with is to actually run my 4-ways in pairs, e.g. for a east-west track like yours, top to bottom, E-W-E-W, rather than E-E-W-W, and then have the junction just on the bottom pair, with the top lines entirely bypass it.

I don't fully understand what you mean about the signalling and parallel lines. Assume that I stick with this theory and just don't end up with too many trains or junctions; is that signalled as well as it can be or should I have extra signals in the little bits that cross or elsewhere?

As for using two opposing pairs, that makes a lot of sense, but I'm struggling to see how Factorio would handle that any better.

[SyncViews]

So, when a train is anywhere in the junction such as that, say where this wagon is, it will block all these other paths (red), that dont cross the train/wagons path. Only trains traveling along the top line are not blocked (green).

factorio-function-1.png (1.87 MiB) Viewed 29788 times

So in Factorio you need extra signals between so that they have separate blocks (note, only briefly considered chain signals, not guaranteeing 100% )

factorio-function-2.png (3.27 MiB) Viewed 29790 times

Having the other paring arrangement means the junction is only the bottom set of lines, it doesn't link directly here to the top ones. It just means a simpler junction, and less trains needing to cross the other lines.

[xBlizzDevious]

-snip-

That was my intended flow of traffic. Clearly I don't quite understand these signals as well as I hoped.

Thank you very much for your help. I shall now go and watch MORE tutorials on signals. Haha!

[xBlizzDevious]

-snip-

Following your example as a guide and walking through it step by step in my head, I think I've come into a bit of an issue. With the tracks laid as closely as they are on my lines, there is no space to place all of the signals because of how picky they are with placement.

I can increase the throughput a small amount with the space available but I can't set it up to allow all traffic to flow as it should. Well... It's a damn good thing I've got FARL installed as these will some major works.

[SyncViews]

Well, you can just make the junction wider rather than the entire line, although yeah, lots of space between to accommodate the curves and signals... I do really hope they get round to making proper path signals and more compact s-bends...

[xBlizzDevious]

Well, you can just make the junction wider rather than the entire line, although yeah, lots of space between to accommodate the curves and signals... I do really hope they get round to making proper path signals and more compact s-bends...

We can dream, eh? 0.13 is supposed to be a big overhaul of tracks and such so perhaps things will work much better then.

[Ext3h]

At least for a double rail, high speed track, I actually found roundabouts working quite well:

circle.png (2.49 MiB) Viewed 29666 times

During peaks, I actually have 3 or 4 trains passing through it simultaneously, and not a single lock ever. It also signals far enough ahead to ensure that trains will at most have to slow down a bit, but never a full stop.

Circles only break if you forget to add the additional straight pieces on the diagonal sections, as the connection will otherwise be faulty.

Oh, and don't be stingy on the path signals. You do actually need all 8 inside the circle, plus the 4 on the entry, to guarantee full throughput. That's still only 16 signals in total - less than on a regular 4-way cross-section.

If you forget the straight sections, you will inevitably end up with ab abomination like this: https://imgur.com/IIlRJwX

[vanatteveldt]

I'm building a pretty large base now (over 5k ore per minute, I'm sure that others have much higher figues), and have no problems getting enough ore in by train with double track (i.e. one lane each way). In fact, I really doubt that throughput problems are caused by the capacity of the straight ends, I would expect that junctions (of either type) are almost always the bottleneck. But a junction can still handle 28 L-CC trains a minute ( viewtopic.php?f=18&t=22794), i.e. up to 84k ore per minute, which is more than I care to build outposts for.

My setup: I have single header trains with one loc and 4 wagons (L-CCCC), and what I do is:

ore unloading

Using the smart trains mod, all trains are set to wait indefinitely until empty (at unloading), so if there is enough ore in storage the train stays in the station. On loading, they wait 60 seconds or until full. This prevents half-empty trains from driving around. Actually, most trains are just waiting at the moment, so train capacity is certainly not the bottleneck, I should probably add more smelters.

Each drop station has a reserved waiting space just behind the unloading area, to minimize time between trains. Next to this there are general waiting bays in the station. Between the unloading and the waiting bays are the 'special' stations, for FARL (automatically loading rails and mining supplies), for a "base builder" train (with lots of guns and walls), for the supply trains that bring guns to the walls, and a "Home" station for passenger trains.

Note that this is a beltless build, so the ore is picked up by bots into storage and to the smelting area. You can also use bots to unload onto a belt system, that doesn't really matter.

rail layout

I have a main line that connects most places, with some roundabouts to allow turning. All stations are on separate branch lines and have a return loop. I try to position outposts at some distance from the main line as the track between main line and outpost functions as a waiting bay for that outpost to make sure the main line is not blocked by waiting trains.

It's stickied, so I'm sure you've seen this thread: viewtopic.php?f=18&t=18621. This one is also intersting:

[xBlizzDevious]

At least for a double rail, high speed track, I actually found roundabouts working quite well:

circle.png

During peaks, I actually have 3 or 4 trains passing through it simultaneously, and not a single lock ever. It also signals far enough ahead to ensure that trains will at most have to slow down a bit, but never a full stop.

Circles only break if you forget to add the additional straight pieces on the diagonal sections, as the connection will otherwise be faulty.

Oh, and don't be stingy on the path signals. You do actually need all 8 inside the circle, plus the 4 on the entry, to guarantee full throughput. That's still only 16 signals in total - less than on a regular 4-way cross-section.

If you forget the straight sections, you will inevitably end up with ab abomination like this: https://imgur.com/IIlRJwX

Thanks for the info, but the first line in my OP was "I've always built my trains with roundabouts". I know how roundabouts work and that's the way I always used them; I wanted to try something different. Either way, your info will likely be helpful to someone else browsing.

[Ext3h]

My setup: I have single header trains with one loc and 4 wagons (L-CCCC), and what I do is:

I wonder why so many players mix LCC and LCCCC trains. Why not just extend the latter one to LCCCCL with both locomotives facing the same direction?

Now both reach the same top speed and acceleration behavior, reducing the likelihood of a stall at a junction even further while remaining compatible with a regular 4 cargo wagon station.

Effectively, the limit on a junction isn't so much train length or a smart design, but mostly speed and acceleration to resume ASAP after a stall. And that's regardless of what junction type, and even more so for the large junctions where even more trains would get stopped in the worst case.

[vanatteveldt]

My setup: I have single header trains with one loc and 4 wagons (L-CCCC), and what I do is:

I wonder why so many players mix LCC and LCCCC trains. Why not just extend the latter one to LCCCCL with both locomotives facing the same direction?

Now both reach the same top speed and acceleration behavior, reducing the likelihood of a stall at a junction even further while remaining compatible with a regular 4 cargo wagon station.

Effectively, the limit on a junction isn't so much train length or a smart design, but mostly speed and acceleration to resume ASAP after a stall. And that's regardless of what junction type, and even more so for the large junctions where even more trains would get stopped in the worst case.

I don't really "mix" them, I just started out with LCC for my first outposts, and then moved on the LCCCC. Since these outposts will not function much longer and the LCCCC unloading works fine for LCC, I just wait till these old outposts are dry, and then add two wagons and set them to service one of the newer outposts. I just can't be bothered to upgrade the station loading at these outposts, especially since one of them was vertical (so my blueprint doesn't work)

Now LCCCCL (or LLCCCC) might be interesting, I guess the throughput of junctions will improve since trains accelerate faster if they had to stop, even though they're a bit longer. OTOH, I use RSO so the rail stretches are pretty long, so it's not extremely important.