What do you think of this interchange?

[odisseus]

This is an interchange between three tracks that go in the same direction. It is meant to balance the load over these three tracks by letting the train choose the least congested one.

On each incoming track, a train can choose between 2 exits of 3 total. In order to make all exits available to any entry, you'll have to build another copy of this interchange down the line.

A train can stay on the track it came from (e. g. 2->2) or move one track to the left (3->2, 2->1, 1->3). Notice that track 3 is to the logical "left" of track 1.

Thanks to exit bays, even if one of the tracks ahead of the interchange is blocked, the waiting trains won't block the other two tracks.

The interchange in the screenshot is built for TL 10. The largest signal distance is TL+3 and could not be less than 8 due to the bridge spanning four diagonal tracks. Replacing the bridge with a tunnel would increase signal distance by 1

interchange-x-marked-fs8.png (19.51 KiB) Viewed 256 times

Advantages of the interchange:
* can be built both with bridges and with tunnels;
* gentle curves;
* balanced exit arrangement.

Disadvantages:
* long signal distance;
* not all exits are available for any entry.

[Benny]

I don't understand where you would use this. Can you provide an example?

[odisseus]

Check out this savegame. In the bottom corner, a variant of this interchange is used as a load balancer before the station.

[Leanden]

How is this more efficient than a 3 tile PBS junction with left hand switches and a flyover?

[odisseus]

I assume you mean something like the junction in the attachment to this post. Compared to my interchange, it has the following disadvantages:

* no exit bays (although they can be added), heavy trains will block exits for longer;
* entries are not equal in terms of exit choice: only center can choose all three exits;
* exits are not equal in terms of choice probability: center is presented ore often and, under good flow, will be chosen more often;

Both my interchange and simple interchange share these faults:
* signal length is TL+3;
* not all exits are available for any entry.

[Leanden]

No sorry i mean like this using Path Based Signalling.

[odisseus]

Indeed, your variant is much more compact. However, it has no exit bays. A heavy cargo train will block its exit forever, and the next heavy cargo train will take forever to get to speed...

If you add double exit bays to each exit, the junction won't be compact anymore. And when you have exit bays, you can just as well make them start before the bridge, in order to save lengthwise space. The bridge will become much longer, but that's ok because the bridge is part of an exit bay now. And that is basically how I arrived at the design from the original post.

[Alberth]

I think the biggest problem is perhaps its purpose, "balancing". The fact that you need to do that implies that before the junction it is not balanced. That in turn means that the 'before' part is not performing as well as the part after the junction. That means you won't push more trains onto the tracks with this junction, since the unbalanced part is not capable of delivering enough trains, and there are no new trains injected in the junction.

Think of a single road delivering cars to 30 high ways. No matter how evenly you spread the cars onto the high ways, you won't get them full as the single road can't supply enough cars. The situation is less extreme here, but the 'before' part is also supplying at its best performance. It won't give more trains due to shuffling them.
In theory, I could instead remove all high ways, and extend the single road, and get the exact same number of cars at the end of the high ways.

Wouldn't the better solution be to balance earlier?


In your case, there isn't much need to balance at all, just keep the 3 tracks completely separate, put the same number of trains on each, and it's already as much balanced as you can get it. Did you try taking out the junction and see if it makes any difference?


Improvements on throughput can be gained by adding buffers before and probably after each platform.