Requesting help with rail junction

[krios]

]I need some help with my rail junction(s).
In OpenTTD i'm a master in making very complicated railway systems that run multiple trains on very few lines.
But in Factorio i can't figure out how it works. i never used Pre-signals in OpenTTD so chain-signals are new terain for me and the regular signals don't seem to function as OpenTTD's pathing signals
My trains constantly block everything and whenever i think i have solved it they start complaining about a "no path". So then i undo the 'fix' and it's all a mess again

THe problem junction

Problematic junction.png (4.25 MiB) Viewed 4967 times

All trains need to go to their respective stations at the bottom and when they return to their outposts they disperse:
1 goes left.
1 goes right.
2 go up.

Bypass

Ofcourse i'm not a complete idiot and for the 2 trains that go up i build a bypass between the problematic junction and the palce where their routes split off.

Bypass.png (4.53 MiB) Viewed 4967 times

Honestly, i'd kill for the pathing signals of OpenTTD, easier to understand and use in my opinion.

[Serenity]

Not a solution, but it's far easier to have a two lane system once you go beyond a single train going back and forth. Takes a bit longer to set up, but you can easily blueprint a straight section, a diagonal one, curves and intersections.
Two lanes three track-width apart. Big power poles in the middle.

With the upper one, I think you need a chain signal at that tiny straight bit between the forks. If only to make trains reevaluate their path there

[bobucles]

A self imposed challenge? Sounds like fun! Quick question though. Why does the bypass split into twin 2-way tracks? It may be simpler to give each direction a reserved lane.

It looks as though there is no free parking for southbound trains at the bypass. Both southbound paths have a chain signal that flows all the way through, so a southbound train will never enter the bypass and wait for another train to go north. Use normal signals to give southbound trains a parking space.

[Zavian]

See viewtopic.php?f=194&t=53937 for a tutorial focused on designing and signalling two way tracks.

[aober93]

That bypass should be one directional, because a train coming from either direction shall pick a side which the other doesnt. So they can actually pass each other. At the moment both lanes have 2 signals at both ends ,making it 2 directional so a train can enter either side. Thus it can block the other train. 1 directional segments have only 1 signal in the direction the train should go.

But what you will then need is at the merge before and after the bypass, you will need 2sided signals which will make that segment into and out of the bypass 2 directional again.

Chain signals is another story but dont mix em up

[krios]

A self imposed challenge? Sounds like fun! Quick question though. Why does the bypass split into twin 2-way tracks? It may be simpler to give each direction a reserved lane.

It looks as though there is no free parking for southbound trains at the bypass. Both southbound paths have a chain signal that flows all the way through, so a southbound train will never enter the bypass and wait for another train to go north. Use normal signals to give southbound trains a parking space.

The byass splits into a twin 2 way track so a train going up or down can take either direction... i have realy no clue how all of this works as i can't relate it to my OpenTDD expereinces. so i'm just dicking around and hope shit works (wich it often doesnt, that's why i came for help)
Also, what do you mean by the last part? i should change the chain signals to regular signals? but won't it screw up at the junction then? like, if one train was going from the station (south) to it's destination (north) while another train coming from the north going south to the station. One of those trains has to wait at his current bypass or it blocks the entire thing... Could you perhaps give me some visual aid please? i have an easier time understanding what you try to explain that way ^-^

[Zavian]

As others have said the signalling for the bypass looks wrong to me. See the link to a two-way rail tutorial (viewtopic.php?f=194&t=53937) I post earlier for an example of proper bypass signalling.

Edit: added an image from that tutorial of a properly signaled bypass.

[krios]

Aighty, thanks all
I'l look at the turorial and post a litle update to tell ya if i got it fixed or not ^-^

[Aeternus]

Simple rule of thumb for chain signals:
- Chain signal should be used whenever you enter a shared section (including splitting a still shared section). They will reserve the shared section across the entire path the train intends to take and deny a train to enter it unless it is able to exit it. This prevents a train from getting stuck on the shared section and blocking it.
- Normal signals should be used when exiting a shared section.

[krios]

So i promised an update with my newfound naalidge.
After a bunch of dicking around i solved it by removing the train block between the bypass and teh junction.
I feel dumb now. Neverthelesss i learned a few things.
Now with that problem solved i encounterd a new one.
Remember that bypass?

old bypass

Oldbypass close up.png (577.9 KiB) Viewed 4855 times

Trains were somehow waiting in the red circle whenever someone was nearing the junction down south.
So i added a dummyblock

dummyblock

Dummyblock.png (3.38 MiB) Viewed 4855 times

That solved my problem, but it's an ugly solution... eh, if it works it works i guess.
Again, thansk everyone for your help!

[bobucles]

The dummy block is because of how chain signals work. I guess it's my fault for explaining things wrong. A rail signal looks at the next length of track and says "all clear" or "wait here". A chain signal pushes that "wait" position further back, saying "wait there instead". What you get is the space between a rail signal and chain signals behind it is "untouchable", I.E. a train will never wait in between these spots. That bit of magic is what keeps a junction clear and lets trains flow through.

Where I goofed is that trains wait in FRONT of regular signals. They'll drive all the way to the end of that block until they can't go anymore. So place a regular signal BEFORE a spot you want a train to park. Chain signals push the end point backwards, so that trains won't creep into intersections while they wait.

The general rule of 1-way junctions is to place a full signal after the junction, and chain signal all the way back. This still applies to setting up a bypass, but the junction is the "Y" that opens into the bypass. See the pic. I got it to work without the "redundant" chain signals, but this tiny setup worked either way.

factorio train junction.jpg (377.76 KiB) Viewed 4833 times

[Zavian]

The bypass really shouldn't consist of two two-way tracks, but of two one-way tracks. With 2 two-way tracks you could have 2 trains coming from the south occupy both the track of the bypass, meaning that a train approaching from the north direction can't get past, and you have a deadlock requiring manual intervention.

[LazyLoneLion]

Again there was a brilliant rule of thumb there, it will definitely help you.

Before the shared piece (on the entrance) put the chain signal. After the shared piece put the regular signal (on the exit).

Explaining in details:

On the entrance to the split should be chain signal, so no train will stand on the split itself. On the opposite side of this signal should be regular signal, because the train that is exiting the bypass is freeing the whole contraption and isn't mixing with anything on the bypass.

Just after the split there should be the regular signal on the direction exiting the split and chain signal on the direction entering the split. Same principle on both splits on both ends of bypass. Although it's much better to leave one-way bypass pieces. The principle is the same -- chain signal on entrance, regular signal immediately after, on the exit.

And even better is to use two-rail one-way system.

And you'd better have signals outside the bypass (generally speaking they are not redundant, although they could be farther along). The same principle -- chain on entrance direction, regular on exit direction, both sides of the rail (until you have two-rail one-way system -- then you'll need no "bypass" except for stations).

Just try it and you'l see how beautiful the principle is. And how easy to understand.

[JimBarracus]

But in Factorio i can't figure out how it works. i never used Pre-signals in OpenTTD so chain-signals are new terain for me and the regular signals don't seem to function as OpenTTD's pathing signals

Is it still a mystery to you?
Functionality and layout are almost the same.