Efficent intersections of two double tracks. (right of way)

[carlthuringer]

Hello, sorry to post so soon after the first, but this being a separate topic I didn't want to clog the first post with this request.

When two perpendicular lines, each composed of two one-way tracks, intersect, what is the most effective way to manage all the possible turns a train may need to make?

What strategy should one use when optimizing for efficiency?

What strategy works best when building for a high-traffic, indeterminate future?

[Combuijs]

I didn't want to clog the first post with this request.

Much appreciated.

What strategy should one use when optimizing for efficiency?

Don't know what you mean exactly with efficiency (when someone is optimizing then you may hope it is efficient  ).

For a simple crossing see the answers to your own post in the archive: http://archive.forum.simutrans.com/topic/07382.0/index.html

For a high-traffic crossing use bridges or tunnels like:

[VS]

You could make it a little bit more jam-safe by lengthening the intersections and signalling them to the used train length, thus creating small "waiting spaces" for trains that can't enter the other track immediately. Of course the longer they will be, the more trains can wait there...

[yoshi]

Just an example.


http://yoshi.simutrans.com/gazou/intersection.png

It's important to branch off the tracks, before the points where other tracks merge. Otherwise, trains which don't need to share a track, will be forced to share the track and lower the efficiency of the intersection.

[VS]

Yup, that would work nicely

While posting in your other thread, something else popped into my mind:
http://vs.simutrans.com/remote_images/tracks/simscr04.jpg
http://vs.simutrans.com/remote_images/tracks/simscr05.jpg
I think it's actually 9 different routes intersecting. Besides the visible mess, there is another layer of spaghetti in tunnels in these small hills. And it works. So, don't fear "organic" designs

BTW, the complexity is increased a lot since some parts are for driving on left and some on right! (Or ccw and counter-ccw loops.)

[carlthuringer]

Combujis: I use that exact design. It's a pretty logical one for starters and it does work for a long time. However, the fault is that left-turning trains must cross over the intersection space twice. Once to go over/under, and once more after taking that short right loop to go under/over again. In the end, they slow down trains that would otherwise be able to simply cruise through the clean straight-through tunnel or bridge.

Yoshi: Seems like your design alleviates the left-turn problem, at the expense of being very large. I've done a similar layout, though I prefer tunnels to bridges, and it works quite well. Just big.

VS: Wow, I'm mesmerized... So as you build more lines, do you just hook them up in the directions they need to go as you're building? An organic approach to track-laying seems very Zen. Flow with the land.

[VS]

Hehe, I wouldn't put it that way. I played this game on small map, and there wasn't so much space to use to begin with. The depicted area is right in the middle of this map, to the left of text "Bílovice":



As you can see, it is so heavily covered in houses that there wasn't much of a chance to build any proper crossing at all.

What I wished to show is that you don't always need geometrically clean crossings. But then invest in some spare horsepower when buying engines, so that they drive reasonably fast over the "bumps".

The map is 384x384. If I played on 1500x1500 (15x more area), I would never face any space issues and happily use yoshi's solution, maybe even biggerized to the point where more trains could fit on intersections.



Also... Combuijs' solution is almost optimal. However using bridges instead of tunnels has a hidden advantage. It's a really hardcore tweak and only theoretical, I never bothered with it, but here it is anyway: If the train goes upward, it slows down and "some energy is lost". Then again when it goes down a slope it speeds up. Assuming the train is arriving at full speed... When you make the train drive over a raised bridge, it first climbs and slows down. Kinetic energy is lost to potential. Then it goes down and it is converted back. There is some loss due to "clipping" of the speed; the train accelerates again on the bridge a bit, adding some small number to the total E. However when you use tunnel, it could speed up - but there is the speed limit and the "gain" from going downhill is lost. So there

[carlthuringer]

Aha! I didn't think about that but you're right. You don't gain speed going downhill if you're at the max, and then you'd end up with a lower net speed leaving the tunnel.

Besides being aesthetically pleasing, tunnels that dip briefly aren't good at all!

[VS]

Well they cost more, too