Factorio Forums

So... when using interrupts, sometimes a situation arises where there's some kind of collision somewhere... and the tracks are blocked, as a result of which one station becomes unavailable to the general network.
In this situation, all the trains go crazy trying to rush there.
UPS drops to about 30. (If you demolish a couple of stations at this point, there will be 2-3) (I have 381 supply stations)
If this doesn't happen... UPS is around 60, well, with occasional drops to 45-50.
But it's not just about UPS...
In general, it would be great if interrupts had a condition like "Path to station blocked" or something like that.

And even better if the map showed the exact location of the culprit station.
Sometimes it takes over an hour to figure out where exactly it happened and why. Perhaps we should add a huge icon to the map that says THIS station is unavailable.
So that it's impossible to miss.

Well, I'd probably be partially satisfied, but I'd be satisfied with a solution that allowed trains to ignore this problem.
Well, of course, ideally, there would be a quick way to find out which station is causing it...
The idea that ALL stations are unavailable is a lie. I've encountered this problem about 10 times already, so one station is unavailable... and that's it.

No, well, of course I can just set up a timer interrupt.
But that doesn't solve the root of the problem; it's a workaround.

Your ups dropping is probably not a result of the train situation but instead because of the 8.8k ghosts awaiting to be built. I remember dev responses that in general say: "don't massively put ghosts you cannot build"

About trains and "no path". This many unreachable reports point to one disconnected station that might only show up if there are multiple stations with the same name and at least one of these is not reachable from everywhere. If all reachable station with this name are closed/all slots occupied, and the one disconnected station with this name is the only one still open, the "no path" error will start to show up. If reachable stations with the same name will open up, trains will repath there and the "no path" symbol will vanish.

The general approach for this is as well: "don't do this". Take care while building stations and don't build disconnected ones. You made your issue hard to find by just stamping cityblock-style blueprints without probably checking if everything can really be built, so some station might have been built but not connected to the main rail until all ghosts are built as well. It may be it's just one single signal missing, not even some rail track.

However the "no path" isn't necessarily an issue. It's just a visualization, some notification. But not an error message. If there is just one disconnected station, the trains will find a new path as soon as some other reachable station with the same name as the disconnected station opens up.

About interrupt: there is the interrupt condition: "destination full or no path". This interrupt is able to redirect any train with the "no path" condition to some known station.

To understand your last screenshots it would help if you make it while your game is set to English. The letters you use are incomprehensible symbols for most of the forum users. I even create my station names in English although my native language isn't English, so in case I post screenshots on the forum people are able to understand what the station purpose is.

Your game is modded, and it seems you use some train mod. It's also not clear what behavior this mod will change from the vanilla game.

So, after 40 minutes of searching, the culprit was found. 25-30 UPS We put the rail back in place. Instant growth up to 60.
After a couple dozen such cases, you can't help but wonder: couldn't these stations have been illuminated?

Tertius wrote: Thu Jan 29, 2026 10:17 am Your ups dropping is probably not a result of the train situation but instead because of the 8.8k ghosts awaiting to be built. I remember dev responses that in general say: "don't massively put ghosts you cannot build"

hedgehog499 wrote: Thu Jan 29, 2026 10:25 am After a couple dozen such cases, you can't help but wonder: couldn't these stations have been illuminated?

Not sure if by "stations" you mean "tracks," but there's no way for the game to know whether you broke a track connection accidentally or on purpose. It would be annoying if the game flashed an alert every time you didn't have continuous tracks.

Tertius wrote: Thu Jan 29, 2026 10:17 am Your ups dropping is probably not a result of the train situation but instead because of the 8.8k ghosts awaiting to be built. I remember dev responses that in general say: "don't massively put ghosts you cannot build"

I remember this same problem quite clearly about a year ago, with the vanilla version.
True, it wasn't on such a large scale back then.
The problem with UPS is clearly the simultaneous route search requests from hundreds of trains, across hundreds of stations.
You say it's not a bug...
But I would strongly avoid it.
Any "Destination busy or no route" condition doesn't negate the fact of an excessive, suboptimal search.
I assume there's a loop through the entire train list/array, for each train.
More like a train graph, but that's beside the point...
This operation is extremely expensive for the engine; overall, I have 1,240 stations and 1,667 trains.
Which is largely my own fault... Most of them are depots, and such a large number of trains is due to the automatic train spawning system, which I barely got going. The train mod will only add a different type of train fuel (a separate battery type), but the engine and handling will be identical to vanilla.

In short, there's plenty to think about.
With a certain combination of interrupts, it seems possible to significantly mitigate the negative effects.

However, this doesn't negate the possibility of a hint indicating a station disconnected from the main network. The "just don't do it" argument still doesn't negate the fact that the game knows where the station is, but doesn't tell you.

Kyralessa wrote: Thu Jan 29, 2026 10:33 am

hedgehog499 wrote: Thu Jan 29, 2026 10:25 am After a couple dozen such cases, you can't help but wonder: couldn't these stations have been illuminated?

Not sure if by "stations" you mean "tracks," but there's no way for the game to know whether you broke a track connection accidentally or on purpose. It would be annoying if the game flashed an alert every time you didn't have continuous tracks.

I use Google Translate, so that's probably the issue, so I have no idea what it means.

Basically, yes, it would be annoying.

Still, it would be worth adding a setting... to show or not show...
and, since that's the case, turn it off by default.

hedgehog499 wrote: Thu Jan 29, 2026 10:40 am Any "Destination busy or no route" condition doesn't negate the fact of an excessive, suboptimal search.

You provide a small grid with very short blocks, so there is a huge amount of blocks to check and a huge amount of alternative routes. The game is using the A*' search algorithm, which is considered "optimal" in most cases.
Computing complexity increases exponentially with b^d where b is the branching factor (huge for cityblocks) and d is some depth that is also high for a setup with many (but short) paths. Also see https://wiki.factorio.com/Railway/Train_path_finding

So I still say: "don't do that". The game engine isn't able to perform a miracle.

Tertius wrote: Thu Jan 29, 2026 11:06 am

hedgehog499 wrote: Thu Jan 29, 2026 10:40 am Any "Destination busy or no route" condition doesn't negate the fact of an excessive, suboptimal search.

So I still say: "don't do that". The game engine isn't able to perform a miracle.

So, most of the code is excellently written, and sometimes it feels quite capable. In general, the performance can be surprisingly good.
Well...

What if you add loops to all the dead ends and remove all roundabouts? I would experiment myself but you haven't posted the save.