Rail junctions

[vanatteveldt]

I've been playing factorio for a couple weeks, and I'm trying to optimize some of my designs. I play with smart trains, RSO, and FARL to get some more rail action.

I started by building basic roundabouts for my rails, with a signal going on and off the roundabout, but the whole roundabout as a single block to prevent deadlock.

Next, I added shortcut tracks for the most used directions, e.g. often straight on a roundabout that is mostly meant as a turning point for a nearby outpost, e.g. like so:



Now, I have a "central station" in my main base (which does all smelting and manufacturing), with a junction immediately east. I've added shortcut tracks for ever direction to come/go, which is made slightly more complicated by the fact that my oil drop off is located to the south, so the south to north and east also 'need' a direct connection:



West is my main station, South is oil dropoff and outposts, East and North are outposts. (Edit: never mind the broken track, I had fun with my flamethrower when the biters interrupted my screenshot taking...)

(note that my trains drive on the left, god knows why. Also note that I started with a very wide space between the tracks because I didn't understand junction design, my new tracks are all spaced 4 apart with a pole in the middle)

Questions

1) Is my basic thinking correct, that the more track I add the quicker my trains leave the single-block junction, so the better?
2) Are there better designs, e.g. with multi-block junctions or external shortcut paths? I found designs like this: https://dl.dropboxusercontent.com/u/486 ... uction.JPG (from https://www.reddit.com/r/factorio/comme ... _possible/), but that looks like there would be deadlock conditions. I would rather have a slight inefficiency than a chance at deadlock that needs manual intervention...
Edit:
3) I guess I can also just get rid of the original roundabout now, since all travel directions are taken care of (and I would never need to turn around just outside the main station). But I guess I can also leave it in cause it's kind of pretty...?

[gheift]

Do you use 0.11.x or 0.12.x?

[vanatteveldt]

Factorio 0.12.17 (Build 17307, linux64)

mods:

Code: Select all

FARL_0.4.41.zip
rso-mod_1.4.6.zip
ScienceCostTweaker_0.12.10.zip
SmartTrains_0.3.7.zip
STRS_0.0.5.zip

[SirRichie]

I find the traditional roundabout without shortcuts to be pretty effective, when used with chain signals.

The basic idea is that you separate the circle with 4 chain signals (top, bottom, left, right). In addition, you place a chain signal before the roundabout on the incoming lanes (there should be 4 incoming and 4 outgoing lanes per roundabout).

This way, you have an easy, deadlock-free version, which allows for 4 simultaneous trains in the ideal situation (4 trains going right on a right-lane traffic). If trains want to go straight, still 2 can pass the roundabout at the same time.
You can, of course, possibly enhance this design with shortcuts, but that makes signal-placing much more complex, so I do not use that.

[SpeedDaemon]

Having the whole junction being one block is terrible for train throughput. There's only a few situations when a train would really need to stop, but being only one block forces stops any time there's more than one train.

I generally design my train network to avoid 4-way intersections entirely. 3-way are much easier to keep clean, and easy to signal properly, as well. Roundabouts are generally bad. Don't know how the idea got started around here, but we're still trying to stamp them out.

Here's one of mine that has a complex network with no 4-way intersections needed. Almost 50 trains on there, and no problems.
http://theharms.org/factorio/bobs-factory/map.png

Learn to use chain signals, as they're essential to avoiding deadlocks and good traffic management.
Have a look at the OpenTTD wiki for more about signalling than you probably ever wanted to know. OTTD "pre signals" are roughly equivalent to Factorio chain signals. The basic idea is that you can prevent a train entering an area unless they can get all the way through, even if you need to put additional signals in between (for example, to separate multiple tracks that must be crossed).
https://wiki.openttd.org/Signals

[DaveMcW]

Ignore the haters, the basic roundabout is great! 8 chain signals, 4 normal signals on the exits.

[vanatteveldt]

Cottages!!!

Sorry, I couldn't resist .

On a more serious note: I like how easy roundabouts are to set up, and with chain signals (and especially the fact the curves don't slow down a train as in RL) they seem pretty efficient, and they are easy to upgrade to 4-way junctions if you start out with a 3-way. However, in most circumstances there is a limited set of directions that train go to (i.e., from outpost to main base and back), so maybe simpler or more situation-specific designs will work just as well?

Edit: do you normally blueprint the complete 4-way system, or do you have a "circle" blueprint and a "onramp" blueprint?

[ssilk]

I find the traditional roundabout without shortcuts to be pretty effective, when used with chain signals.

Indeed I tested around on a very very big map with > 80 trains to replace some junctions with circles. With the chain signals the effect of exchanging it is remarkable (slightly slower) but much less remarkable as with v0.11.
I would guess the difference is about 10-30%, which is in most cases o.k. (compared to 100-200% from v0.11 before) and for all other junctions you may still need a "special solution", cause the traffic is still too high.

[SpeedDaemon]

However, in most circumstances there is a limited set of directions that train go to (i.e., from outpost to main base and back), so maybe simpler or more situation-specific designs will work just as well?

This is normally the case for me, but only until the base gets big enough that I start using a passenger train to get around, at which point you end up going from anywhere to anywhere. But adding those options to intersections usually isn't a big deal, since there would theoretically only be one train using it (and that sporadically).