Source
r/factorio•
Sheant

Mixed LHD/RHD crossing

Design / Blueprint

In https://www.reddit.com/r/factorio/comments/a9tkmz/a_bit_unusual_looking_4way_intersection_design/ecnave5, u/roothorick showed some options for mixed-mode LHD/RHD crossings. I wasn't quite satisfied with his solutions as I prefer 3-apart over 6-apart 2-lane networks, so made one myself:

https://i.redd.it/kq3u3j9pq7721.png

The idea is to build your train network to have vertical tracks be LHD and horizontal tracks RHD. I believe this brings some advantages over pure LHD or RHD modes.

  • Close in compactness to e.g.: https://factorioprints.com/view/-KjYZeRSDZ5gJrR46RYy , but with straight tracks for the straight through directions.
  • More compact than any straight solution for pure RHD/LHD setups that I can come up with similar signaling behaviour/rail block separation.
  • I would have liked to split both cyan railblocks in 2, but don't believe that is possible without making the crossing much larger, but I also don't believe these blocks cause actual issues as the would not be any independent traffic possible if they were split that's not already possible.

Of course, changing to a mixed mode setup has some unfortunate consequences, in that you will need separate blueprints for everything depending on the orientation.

Next up, investigate 4 lane crossings. I think it should be possible to make those even more compact, especially if you're willing to pre-sort traffic in sections before the crossing. By not connecting all ins to all outs it may be possible to make a purely square 4-way 4-lane crossing.

Posted Dec 29, 2018, 12:38 PM UTC · edited

2116
Amadox•

as if LHD isn't weird enough, why would you ever want to MIX those systems? oO

3
SheantOP•

"For science!". This is Factorio, do you even have to ask? Rail crossings are horrible. Anything that can potentially improve them is great.

I've experimented with a grid setup where each line in the grid his single direction. It turns out that even the loops this creates are bad, so I gave up on it. Perhaps try with a larger grid next time, or fewer regular rail signals.

4
Halke1986•

It looks nice!

I'm also interested in performance of mixed LHD/RHD intersections. I've tested your design in the revised testing framework* from the intersection forum thread. After some tweaking necessary to make the framework accept mixed intersection the results were ~42 trains/min in random traffic. Not bad. For comparison, according to revised framework, standard roundabout is ~30, and my favorite "COMPACT" intersection is ~48.

*According to my experience, the revised test framework produces different (higher) results than the original one, so it's impossible to compare its results to official throughput numbers in the thread OP. Or perhaps I've f****d something up when performing measurements.

2
SheantOP•

Ok, you've convinced me, that compact layout is definitely more compact, if it also gives slightly better performance, that's it for this design.

1
Halke1986•

It wasn't my intention to convince you to drop your design. I wanted to put it into some perspective. Mixed intersections aren't well researched, maybe there are better designs possible?

1
SheantOP•

True, true. I did at least still want to look into 4-track versions.

1
Halke1986•

Ah, 4 track version is even more interesting - it can be mixed in different ways. For example tracks can be arranged not only in the standard IN,IN,OUT,OUT pattern but also IN,OUT,IN,OUT...

1
Callec254•

Unrelated tangent, but for us simple folk that will choose one or the other, is there a reason to choose LHD or RHD other than "that's how we drive in my country?"

1
oreida1•

One reason I use LHD is to keep the signals in between the tracks.

2
Illiander•

Signals between tracks/Signals outside tracks.

Only really matters for aesthetics or on tight map layouts (ribbonworld types), since signals between the tracks lets you put them right up against the edge of the world.

1
saltyhumor•

This is an interesting idea but I would confuse the hell out of myself. And what about diagonal tracks? Or 90° turns?

1
SheantOP•

Bah, diagonal tracks are the devil's spawn, and 90% turns are just a very simplified crossing. I always build all my tracks and crossings by starting with a full 4-lane crossing and dropping unnecessary parts for the turns, straight-throughs, T-crossings, 2-lane versions, etc. I always want to upgrade from 2 to 4 lanes transparently, and change a straight to a T. (Don't really use full crossings).

1
excessionoz:circuitblue: Taking a break•

I would hate to try and debug your rails. Sensible people choose LHD or RHD. Mixing them is a recipe for disaster, generally speaking.

It's excellent that you have the choice though. :) Yay Wube for making terrific software that is lane agnostic.

-3
SheantOP•

If it's more efficient, wouldn't it be more fun to try, It's like braiding underneathies. Not pretty, still cool.

3
excessionoz:circuitblue: Taking a break•

You have the choice. Personally, as stated, I prefer rail systems to be either LHD OR RHD, not a mix.

-1