TL;DR
The addition of a negated version of the "Destination full or no path" train interrupt condition.What?
Currently, Factorio offers the "Destination full or no path" train interrupt condition. This interrupt condition is very helpful in preventing deadlocking trains, especially when a station becomes unreachable.However, this interrupt is only useful after the fact a train has already targeted station. A negated version of the condition, "Destination not full or has path", would check if the train has a path to the station before it is planned to go there, as a 'true' condition.
Why?
I want to explain the why using a personal use-case first. Currently, I've designed and built a smart(er) rail network system (the umpteenth person at this point
). The TL;DR of the system is:
- Two types of stations, provider and requester stations. Stations share the same name, so for example: "[copper-ore-symbol] Provider" and "[copper-ore-symbol] Requester".
- Provider stations provide a resource type, and are disabled using a circuit signal for the station 'Enable/disable' slot when no resources are available to be provided.
- Requester stations request a resource type, and are disabled if they are full enough.
- Trains are scheduled using interrupts to go to provider/requester stations. A train will only go to a provider if <cargo is empty AND station isn't full> and the same for requester only if <cargo present AND the station isn't full>.
- If there's nothing to do, go to depot (the only non-interrupt schedule entry). As a failsafe, if the path got destroyed, an interrupt with the condition "Destination full or no path" will send it to return to a depot.
The system works well for my purposes, but it breaks once there are multiple separate rail networks. Once all provider/requester stations within a rail network are disabled, the game's intended logic will try to dispatch a train to a provider/requester outside of the rail network, and is thus unreachable.
An example of this situation in my current blueprint/test sandbox world:
A train in the top-left network is trying to go to a copper plate provider so it can bring resources to the copper plate requester in its own network. The copper plate provider is empty and disabled in its own network, so it gets dispatched to the copper plate provider in the separate network in the bottom-right.
Which brings me to what the new interrupt condition could mean for this use-case:
By the addition of the requested negated interrupt condition, in addition to checking cargo being empty/full and if the station isn't full to go to a provider/requester, a train would only target a station if it could actually reach it in the first place.
Of course, this is just one use-case. I'm pretty sure there could be other situations. I could think of the situation where such an interrupt condition could be helpful for factory planning purposes, i.e. where only part of a rail network is being built in advance, but not yet connected to a full network.
Additionally, I don't think pointing to the LTN mod is the solution here. I think using interrupts schedules over LTN (or some other circuit network heavy interrupt scheduling) is much simpler to built and understand, especially for people a bit newer to Factorio and using trains within the game.
Furthermore, I've tried searching the forum for a same sort of suggestion and found this topic viewtopic.php?t=127380, however this seems to propose changing station targeting behaviour, which for the good measure is not what I am suggesting.
I am happy to provide additional information, save files, etc. or to have an open discussion.