[0.12.22] [Dominik] Train block its own path with chain signals

[Kevin94]

I've found another type of that problem:
Kevin, this is bad design of your rail network. The roundabout should be separated with the signal (more precisely a pair of them so the trains can go both ways). Because you have chain signal it will still not allow any train to go to the roundabout, even if another train is there.

If you haven't noticed there are another pair of signals at the two entries of the roundabout at the track triangle. As posted they are all chain signals and even if the train waits there it can not enter.

As I already sad: the rail network was just in development and not yet optimized. But non the less should it, in my opinion, be possible to enter a block guarded by a chain signal if the train leaves it at the same exit. If the developers don't see it this way this is an issue for path-finding, as such routes must than be forbidden. In my scenario there would have been another, proper signaled, roundabout at the track leaving the screenshot upwards.

[jarcionek]

I've found another type of that problem:
Kevin, this is bad design of your rail network. The roundabout should be separated with the signal (more precisely a pair of them so the trains can go both ways). Because you have chain signal it will still not allow any train to go to the roundabout, even if another train is there.

If you haven't noticed there are another pair of signals at the two entries of the roundabout at the track triangle. As posted they are all chain signals and even if the train waits there it can not enter.

As I already sad: the rail network was just in development and not yet optimized. But non the less should it, in my opinion, be possible to enter a block guarded by a chain signal if the train leaves it at the same exit. If the developers don't see it this way this is an issue for path-finding, as such routes must than be forbidden. In my scenario there would have been another, proper signaled, roundabout at the track leaving the screenshot upwards.

You should use normal signals at all dead-ends. If you had a locomotive on each side of the train, your station could look like this:

Screenshot1.png (780.8 KiB) Viewed 10745 times

Now it doesn't matter whether there is a roundabout at point B or not, there can always be only one train between A and B.

Your case:

Screenshot3.png (1.86 MiB) Viewed 10745 times

Fixed case:

Screenshot4.png (1.99 MiB) Viewed 10745 times

You are going to point out again that you have other connections - that's true but they don't affect this problem, there might be other different problems with them. If you provided a save file I am more than happy to help you with this.

I really cannot see any bug here.

[root]

He said himself it can't happen on its own. This is only possible if your train is manually stopped or runs out of fuel in the middle of your intersection, AND is told to basically do a U-Turn (in this instance go South). Because of the trains length its occupying 2 blocks, which is blocking itself.

The attachment preview.png is no longer available

Normally the train cross this intersection without problems, but if at the moment of crossing I put rail or signal somewhere, the train stuck at intersection.

factorio-train-self-lock-stuck-bug.jpg (672.82 KiB) Viewed 10678 times

[ftbreizhbugs]

He said himself it can't happen on its own. This is only possible if your train is manually stopped or runs out of fuel in the middle of your intersection, AND is told to basically do a U-Turn (in this instance go South). Because of the trains length its occupying 2 blocks, which is blocking itself.

I scribbled over your image to help you understand why its gone wrong.

preview.png

I faced this situation yesterday...
basically, two exit from the roundabound were a possible path and the train was trying to do a more than 360° turn when it blocked itself! Did it recompute its path while inside the turn? Could we have more explanation on the pathfinding algorythm used?

[youdoomt]

I'm not sure if I consider this a bug, if I allow this, it would be possible for a long train to hit itself.

Trains re already able to hit itself in certain conditions, at least they can in MP.
But I have seen the problem many times on the server I play on, and it bothers me cause a train should not do over 360 degree turns in a roundabout right?

[rtssmkn]

Try this design it is, AFAIK, dead lock free...

And, BTW, chain signals work properly only when accompanied by a matching signal, i.e. you need to split your line into segments by using signals and chain signals. Having just chain signals means that they all refer to the same segment in your line, hence the dead lock you are experiencing.

[orzelek]

Quite a few of those normal train signals are not needed.
You don't need to pair chain signal with normal one - normals should be only on exits.
I'm not 100% sure but normal/chain pair might make train stop before the chain one and thats not recommended in the middle of intersection. Having only chain ones means that trains are not allowed to stop there.

[sparr]

Try this design it is, AFAIK, dead lock free...

And, BTW, chain signals work properly only when accompanied by a matching signal, i.e. you need to split your line into segments by using signals and chain signals. Having just chain signals means that they all refer to the same segment in your line, hence the dead lock you are experiencing.

Not only are those normal signals not needed, they are going to break the chain signal functionality. Four trains arriving at that intersection at the same time will deadlock.

[sparr]

Automated trains will NEVER do a 450 degree loop (1.25 rotations)

What if a train is forced to recalculate its path just after entering the loop, due to track being deleted or damaged ahead of it?

[sebaulri]

This Bug still happens in 0.15.9

Bug Screenshot

20170507195428_1.jpg (656.87 KiB) Viewed 10171 times

As far as I can tell. It is occationnally triggered When extending my rail network.
I suspect it only triggers when the Train has already entered the crossing and I finish an alternate ( turning loop in crossing as seen in the sreenshot) route at a remote location.

[warlordship]

I'm getting this as well. I use a simple roundabout. I use chain signals throughout, with a regular signal at the exit:
steamcommunity.com/sharedfiles/filedetails/?id=817978254
HTTP part removed for lack of URL posting capability for first time posts.

Note that this screenshot does NOT show the particular "train blocking itself" error, just what my intersection looks like. In the new .15 version, I have gotten two trains stuck in the loop when they tried to do a 450 loop. At least, that is what it looks like it wants. It seems to happen when I have a LOT of trains blocked, such as what happened in the screenshot. I will come back from building trains on the network to find my base gridlocked, and one train stuck in the loop.

I don't know if it happens because of an error in signalling I missed somewhere, or simply because I add to the rail network half-way across the map while they are paused, and one somehow manages to inch forward to gridlock.

Either way, I don't think a train should re-calculate a route in the middle of a chain signal block unless the rail change affects the particular block.

[l00k3]

Ive had this issue as well, for some reason one of my copper mine trains will start going to its mine and stop randomly across all 3 of my main highway lanes. This means that the train sees the path as blocked and I cant fix the issue remotely, I have to go the the site and manually drive the train onto the correct side before I can turn it back to automatic mode.

[Zavian]

Personally I'm not sure that this needs fixing (although the suggestion of allowing trains to collide with themselves could be amusing).

Pretty much every example in this thread could be solved by better track layout/design and/or better signaling. eg take warlordship's example. Warlordship:The iron station needs a waiting bay or stacker, where trains can wait without blocking the mainline/other trains. At the exit to most intersections(including roundabouts) you should normally have regular signals marking the start of a block that is large enough to fit your largest train, so that a train that enters the intersection is guaranteed to able to completely clear the intersection. The roundabout has regular signals on the exit (which is correct), but the exit blocks are far too short for the trains in use. The entrance to the iron/copper stations is so close to the roundabout, they are effectively one intersection, and should be signalled at such. It looks like you could move the entrance to the copper station, so it branches off the mainline south of the iron station. That should mean there is there is enough space for one waiting bay for both the copper and iron stations. You are also running too many trains in too small a space, since every train is always using at least one block, you can end-up in a situation where there just aren't enough empty blocks for trains to run freely. I suggest you read the first post in this topic viewtopic.php?f=18&t=18621 .

Many of the other examples appear to be contrived examples with an unrealistically long string of pure chain signals, in layouts where you would normally include some regular signals. (And correct use of regular signals and/or minor changes to rail layouts should solve most of those cases). Even the 270 degree left turn that is a three quarters of a loop (ie turn right by turning 270 degrees left) should be fixable by either by adding a regular signal just after the cross, or by building a normal 90 degree right turn.

[sparr]

Pretty much every example in this thread could be solved by better track layout/design and/or better signaling.

Any roundabout will deadlock if four [longish] trains enter at the same time, each attempting to proceed straight. That needs fixing on its own, and it would happen to fix this problem too.

[Zavian]

Save game/screenshot ?

With proper signalling that shouldn't happen.

[DerGraue]

I am wondering as well if this is still on the "will be fixed" list, because I ran into the same problem:


image uploader


This shouldn't be possible.
This situation occured while building some new rails with a blueprint, including some new stations.
The train that is blocking itself did not have to path along the newly built rails (they were not even close along his path) and did not have to visit the newly built stations, they have different names. No rails were removed.
On my map no stations and/or signals are disabled by circuits or anything so the train shouldn't even try to repath.

- In general I think trains should not even be able to block themselves with chainsignals. If someone designs a track with very long trains that crash into themselves because of that it is a design flaw of the track.
- Also, if a train has to repath and has to stop, he should keep his original direction while he is stopping. In my picture the train obviously wanted to make a 450° turn, which could only have occured while he was repathing on the roundabout. And then, while he was repathing he decided for the wrong turn.

This is actually quite important for my base right now, I would have to change my whole design of my base. If a dev would just respond like: "no, we won't fix this" or "yes, but not with 0,16" or something that would be neat.

[Dominik]

Hi, I have added a check of whether the train reserving a block in front is itself and it will work right in 0.16.

[mrvn]

He said himself it can't happen on its own. This is only possible if your train is manually stopped or runs out of fuel in the middle of your intersection, AND is told to basically do a U-Turn (in this instance go South). Because of the trains length its occupying 2 blocks, which is blocking itself.

The devs can't do anything to solve this as everything is working as it should (unless you give temporary powers to ignore signalling). Making trains ignore signals turned red by themselves would result in cases where trains will collide with their tail end. If you still get annoyed by this then to solve it you will have to either make the roundabout larger to accommodate for the length of your trains, or shorten your trains length.
Also a temporary fix as opposed to getting in the train is change the signal in front of it to a normal one for a second.

This does happen on its own. Specifically when a train re-paths due to 1) placing ore removing rails, signals or stations, 2) stations being activated/deactivated by circuit conditions.

Also long trains will collide with them self on a 270° turn in a raoundabout despite chain signals. When a long train reserves blocks it can reserve a block it has already reserved. And then it gets the green light to do a 270° turn and drives into itself. Try it with a roundabout that requires a 270° left turn instead of a 90° right turn shortcut.