Transport Tycoon Forums

Hi there
I'm trying to build a 4x4 junction that doesn't take up too much space AND still be able to "eat" almost anything you throw at it.
My first attempt didn't work out so well (see attachment) - Well neither did my 2nd., 3rd. or 4th. attempt. But I received a lot of comments that helped me improve on the junction .

[EDIT]
In this attempt you can clearly see that I failed BIG TIME with the "doesn't take up too much space" part.. and this is only ONE of the branches..

The latest version of the junction that I'd really like you guys to comment on can be found here.

All (any) comments are greatly appreciated!!

PS.
Is the file size a problem?? - If it is, then I'm really sorry and I'll upload it somewhere else a.s.a.p.



Kind regards


The following is from my original post:

Should I make the branches bigger so they can hold complete trains (7 tiles)?
What kind of signaling would be best??

Any comments would be greatly appreciated.


Thanks in advance..

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The knack of flying is learning how to throw yourself at the ground and miss.
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On enter into branching blocks must be a path signals, of course.

whow - That was fast

What about inside the junction - Should I place path signals in there as well, or is it enough to use path signals "before" and "after" the junction??

Did I make it too "compact"?


Kind regards

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

If your junction is ~16 tiles long and you plase signals only before (path signal) and after (path not necessarly, it can be general block signal) junction then you cause your trains to travel with distantion between them in ~16 tiles. I think, you not planned such result

Sense of path signals:


Two trains at the same time can cross signal block. If they paths not crossing each other. With block signals they can't do this together and one of them must to wait.

Sense of signal density:


On top lane trains can travel with 4 tiles between each other.
On bottom lane they start travel with such density. But later they must to stretch interval

So, on straight lines in junction you need to place signals with desirable density for you.

You may ))
But as you say, it is better to hold whole train in branches.
It is easy to do in some branches:

Actually I didn't consider placing signals along the track like that Don't know why I didn't think of that.. (please don't comment on that ) haha



Think I'll have to redesign the junction a bit - Stretching it a little in all directions..


Thanks man - Great input

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The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

You have some merges before splits, which can be a severe hindrance.

Thanks for your reply



Erhmm - I'm not quite sure where you see them??
If I follow the main lines from the start, all I get is "split before merge"..
If it's the mains that goes through the tunnels, then "the split" is before the tunnel and "the merge" right after the tunnel.

BUT, I'm currently working on a few new designs (new to me anyway), without bridges and with signals placed 4 tiles apart. Also it's not as compact as this one.

Less is more, they say... Well not this time!


Kind regards

Ps. Should I modify the original post and let people know that I'm working on a few OTHER designs at the moment?

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

This should clarify the issue.

What about these two splits?? (the "orange" ones)..
The yellow line is split before it merges with the cyan line and the cyan line is split before it merges with the yellow line.

But I see your point. Swapping the two will fix the issue (and complicate the junction a bit more) - The cyan line will then split one more time before merging with the yellow line. I'll try to incorporate "the fix" into the the new designs that I'm working on.
There's also a "merge before split" on the inner track...



AND - Maybe I should read the openTTD wiki again

Thanks for your input

Kind regards

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

I find two instances of cyclic dependency in your intersection, marked with blue and pink in the attached image. The blue one is most severe as it is very short and thus have high chance of locking up your intersection in a cyclic dependency. The pink one can also cause lockups.

So your idea to do split before merge at some places are good. With that technique you can break these two cyclic dependencies and improve the stability of your solution.

_________________
My OpenTTD contributions (AIs, Game Scripts, patches, OpenTTD Auto Updater, and some sprites)
Junctioneer (a traffic intersection simulator)

They are fine, and indeed come before merges.


The cyan line splits, merges, splits and merges. What you'd want is splits, splits, merges and merges. This way any trains turning to other directions won't block and aren't blocked by trains incoming to merge with that line. You want all of the splits before any merges.

I'm not really sure what you mean by "cyclic dependency".. It sounds like a bad thing though.
Does it have something to do with the fact that this junction works somewhat like a roundabout (which can cause lockups)?


Yes this junction is a bit too compact - That's why I'm currently working on a "stretched edition" with correct signaling, enough track for a whole train on each branch and (as of now) with ALL the splits before any merges.



Once again, thanks for all your comments!


Kind regards

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

Yes it does, the most famous example being (as far as I know of) http://en.wikipedia.org/wiki/Dining_phi ... rs_problem.

They have to dine in a train, of course

Of course

And Arie-, thanks for clarifying

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The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

Here we go again

This is the new version of the 4x4 junction that I've been working on. I tried making it somewhat compact but still functional.
Any comments will be greatly appreciated.

The shortest branch leaving the "inner" main track (split number two) SHOULD be able to hold one complete train with a length of seven tiles - But I'm not a 100% sure that it will, haven't tested it yet.
Also, I'm not sure that it's a good idea that the trains can switch track on the main lines. I only placed the "shunts" there so a train on the main line wouldn't have to break for a train entering the main line from one of the branches..

Thanks in advance

[edit] Here's a small version of the attachment below



Kind regards

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The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

Hello again
I hope this post doesn't put me in bad standing or anything like that, but I'd really appreciate any feedback on the above post. I'm not quite sure how to improve on the junction.

Thanks in advance

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.

By making the whole intersection bigger, you can gain distance between split and merge with space for one train to wait for merge without blocking merging trains. However, that will make your intersection larger, so it might go against a goal to make it no larger than necessary.

It all comes down to what traffic pattern do you have and what is your goals.

_________________
My OpenTTD contributions (AIs, Game Scripts, patches, OpenTTD Auto Updater, and some sprites)
Junctioneer (a traffic intersection simulator)

THAT was fast!!!

Thanks Zuu

What about the "shunts" that I placed just before the merges - Won't they some what prevent that a train can block?


Kind regards

_________________
The knack of flying is learning how to throw yourself at the ground and miss.
Douglas Adams.