One '8-Way' Junction

sultana · Post by **sultana** » 14 Jun 2006 07:37

The 4-Way version of this, made by Zimmlock is here, with the OTTD version on some later page.

The goal is, of course, to build one 8-way junction in the square in the center.

The savegame is version 0.4.7.

Some things:
- There's a 126x126 square to build the junction in (was meant to 128, but I counted out 64, not 65), so there's A LOT of room to work with.
- The small hill is the center of the 'junction' square
- I've built monorail stations in a city in each of the 8 sections.
- Next to Sydney are some depots with trains in each of them, there's 28 trains (one between every city) with orders on them to make sure the junction works

- (After I built my junction with waypoints, I added them to the orders and cloned all the trains once so I had 56 trains (14 per city) which seems to work pretty well.)
- Power Station: South West (near London)
Steel Mill: South East (near Sydney)
Sawmill: North East (near Chicago)
Factory: North West (near Amsterdam)
Oil Refinery: West (near Ho Chi Minh City)
(Those are so if one of the industries closes down, you can replace it in the right spot).

Some Rules:
- You can't destroy the lighthouses or antennas
- A train entering from one section must be able to go to any other without having to leave the junction section (which is what the passenger trains are for).
- I would say you have to service every industry, but the map is rather huge. So if this every gets judged or something, this'll be a rule

If there are some rules you someone else can think of just tell me.

Some Things I'm Playing By:
- I was playing with realistic acceleration off without realising it and it does seem like a bit more of a challenge, as the trains slow down massively on any hill, but whatever works.
- No breakdowns

I'll add a pic of my junciton (without actually giving what it is away

) and also a clean version of the scenario (without the stations/trains) I added if you want to play it from the start (that is, without cheating).

Also, there are some tropical trees because I made the whole thing in that climate without realising it. So I had to load it and cheat the climate to temperate.

sultana · Post by **sultana** » 14 Jun 2006 07:43

And seeing as I'm fairly sure there's still the 3 limit on attachments per post, here's a screenie of a small section of part of my junction.

I doesn't really need to be that huge, but I had A LOT of time to make it. That was probably my 4th-5th attempt at it.

sc79 · Post by **sc79** » 14 Jun 2006 08:59

Couple of things;
1) You dont list a version. The scenario loads on any, but you'll get some gameplay differences depending on which version is used.
2) Just looking at the map without playing yet, I'm extremely doubtful that you can funnel enough trains through the single track sections (one each way on most) to make use of the huge junction area. But I guess we'll see.
3) Realistic acceleration has its own challanges (longer corners etc)

sultana · Post by **sultana** » 14 Jun 2006 09:13

Argh yeah forgot that, the savegame is Version 0.4.7

Also, I've got abit more than 160 trains running through my junction in my current game with almost no delays, the only problems come from merging to leave the junction, and none from entering it.

About realistic acceleration, it does have its challenges on curves, but rather then slowing down to 200ish km/h over a 5 tile curve with it on, trains slow down to 50-60ish km/h up hills with it off.

(Though yes, I guess if it was needed you could destroy the a couple of the antennas to open up the junction entrances abit, we'll see what happens.)

Sebastiaan · Post by **Sebastiaan** » 14 Jun 2006 14:10

Well.. i just made a 8 way variant of a classical 4 way type. takes about an hour. Although, i must say, i would have appreciated a copy paste feature for this

Thijs · Post by **Thijs** » 14 Jun 2006 23:10

My try, i went for a more compact solution. About 170 trains running on it with no problems. (28 are still in the depot for copying)

Sebastiaan · Post by **Sebastiaan** » 15 Jun 2006 05:12

Whow. I really like that one!

sultana · Post by **sultana** » 15 Jun 2006 06:19

Sebastiaan wrote:Whow. I really like that one!

Yeah me too. Kinda makes me feel like I made mine too big as I've also got 170ish trains going through it.

Here's two pictures of mine, I tried to get the whole thing, but then I would cut off some of the entrances, but it's symmetrical anyway so it's basically the while thing.

And the other picture is zoomed in around two (kinda) of the entrances, trains drive on the left hand side.

I'm not sure if the trains need the waypoints, they're mainly there for my benefit.

Thijs · Post by **Thijs** » 15 Jun 2006 10:01

I always try to make junctions as compact as possible. But this one is not perfect yet.
1: If i stop a train at a certain point it is possible to jam it (but quite hard though)
2: The diagonal tracks (trains coming from the NE, SE, NW and SW) have a slight advantage over the other tracks as they can trave through the center.
I wonder if i can improve the capacity by signalling. For sure it could be more compact using the path based signalling, but maybe the use of pre-signals could also improve it.
It would be a nice competition on itself to see how many trains can run over this junction fluently, by making improvements to it.
However, due to the two track restriction it is not possible to run more than say 250-300 trains in this scenarion anyways because not only the junctions, but all the tracks would be jammed.

And don't you just love to watch the trains round-a-bouting on a big junction like this one?

^Cartman^ · Post by **^Cartman^** » 15 Jun 2006 11:15

What about this junction-less crossover, covering 128x128 squares?

http://www.tt-forums.net/download.php?id=39135

http://www.tt-forums.net/download.php?id=39133

I have just made a new, maybe even more advanced crossover (128x128 squares crossover on a 2048x2048 squares map).

The pictures shows hardcore testing of the crossover with 280 trains (each with 4 eurostar engines and 24 armoured vans). Every track is tested with 5 trains, all 8 directions have 7 tracks each way, but the tracks are so far away from each other that tunnels with one track between the tunnels can be built.

Now it is time to use the tracks for real traffic, that would be sweet!

I am using the OpenTTD integrated nightly build r3090I4.5.

Thijs · Post by **Thijs** » 15 Jun 2006 13:03

i made some improvements, now 200 trains are running on it without a problem. It's really the most beautifull junction I have ever created

proudmoore · Post by **proudmoore** » 15 Jun 2006 14:27

Nice touch having you HQ in the middle there... now we just need to be able to build statues or something to stick on small islands around it...

Sebastiaan · Post by **Sebastiaan** » 15 Jun 2006 14:41

Thijs wrote:i made some improvements, now 200 trains are running on it without a problem. It's really the most beautifull junction I have ever created

I have a further suggestion: you can eliminate a few tunnels on your outer round-a-bout. All trains leaving it are forced through a tunnel. If you remove that tunnel and switch both exits you gain a level switch and some more place.

If you don't see where I'll post a picture.

Thijs · Post by **Thijs** » 15 Jun 2006 15:39

You're right. Those tunnels are still left from a previous version. At first the junction was a little different, and they were needed. I was a bit lazy, and with realistic acceleration the level changes don't reallt matter. I'll change it later on.
Just after i posted it i did a little test, i stopped a train just before entereing the junction from each direction, and when all trains were stopped, I let them go all at the same time. To my surprise this wasn't a problem, no jams whatsoever. If i remove the inner roundabout the second (from the middle) roundabout can get jammed. The inner roundabout, though it has a lower capacity, resolves that. For some reason trains crossing the junction straight, from say SE to NW, don't take the inner roundabout, only trains making a 3/4 or 7/8 turn use it. If a train is already waiting those turns are made using the second roundabout. At first i intended not to have a roundabout in the center, just straight crossings. But when i lead this around the HQ trains stopped using it and preferred the other way, very strange.

hertogjan · Post by **hertogjan** » 15 Jun 2006 15:42

Are you sure that the roundabouts don't cause jams?
They may jam if there are too many trains. Also, when you use longer trains, traffic jams on roundabouts are more common.

Thijs · Post by **Thijs** » 15 Jun 2006 15:47

with longer trains jamming could be possible, didn't try yet. But the test I described puts the maximum load on the system, and the way I designed it makes it that no more trains can enter the system than can exit it. It there are too much trains, cue's will appear at the entrance of the system. If you don't belive me, please prove me wrong, i added the savegame. Also I just thought of another improvement, which i will try when i get home

Thijs · Post by **Thijs** » 15 Jun 2006 18:14

added some extra track, now the capacity is even larger.

hertogjan · Post by **hertogjan** » 15 Jun 2006 20:53

I also took an attempt at an 8-way junction. I built two versions. They are based on the same idea. It looks like a roundabout, but it isn't, as there are no loops. The idea is best illustrated in the first version (the one which is named 8way1.png). If a train enters the junction, it takes the n-th branch of the entrance track, is it wishes to take the n-th exit. For example, if it wishes to go the fourth exit, then take the fourth branch of the entrance track. The tracks through the junction spiral outward.

The first junction is not that compact. It could be made smaller (5 tiles in both directions) without changing its desgin radically.
The second one is somewhat smaller. It is based on the same idea, but instead of 8 spiralling tracks, it uses less. Depending on which side you enter, the tracks for 2nd/3rd, 4th/5th, 6th/7th are combined, or the 1st/2nd, 3rd/4th, 5th/6th, 7th/8th* exits are combined.

The beautiful thing about this design, is that you can also use it with a different number of exits. You will probably need more tracks, or use a clever combination like in the second design to reduce the size. But the principle of tracks spiralling outward is applicable to any number of exits.

I have not tested the designs, but I know they will work. I have to remark that neither version contains sharp curves, and trains have to climb a hill only once at most. A disadvantage is that if a train goes left (like 6th or 7th exit), it needs to go all the way around, which may be a long journey. But there is enough space in the middle to make shortcuts for busy directions.

*We do not need an 8th exit, as it is the way back, but it appears automatically in this design.

sultana · Post by **sultana** » 16 Jun 2006 12:05

Well I connected every coal mine/iron mine and forest which I placed in the scenario. There's a couple of spots where the tracks merge which queue up abit (with realistic acceleration off). With it on it seems to somewhat reduce the queues at the merge.

There's 260 trains runnning on it, and I think the exit points (more so then the entry ones) have just about hit the limit of what they can take. But I'll try connecting up the rest of the industries and actually try and move all the goods from sawmill and steel from the mill. They could take another 5 or so 10 tile trains each probably. And I haven't even tried to move goods from the factory.

Thijs · Post by **Thijs** » 16 Jun 2006 12:52

I like you're junction hertogjan, it is the best solution imo, as it is impossible to jam it and gives maximum capacity.

If you put 300 trains on it, it will just jam at the exits, letting all trains sit in a giant traffic jam. Can you test if the second option has a lesser capacity then the first? I can imaging the entrance and exit tracks are the bottlenek's anway. Maybe the scenarion should be adjusted to 8x4 tracks, in stead of 8x2.
I put 270 trains or so on my junction, and then it starts cloging. Only from one direction though, where the factory is. (most trains by far)

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