Trucks trying to path to unreachable target when other targets available

Issue description

Trucks repeatedly try to path to targets that are not reachable when there are other, reachable targets that accept the same dump materials. As a result, they get stuck.

Reproduction steps

1. Setup a dump zone with "green" zones at either end (i.e. across water to an island)
2. Get a bunch of trucks to start dumping.
3. Trucks will eventually get stuck trying to reach the far side.

Game version and build number

v0.7.6a (b466)

Operating system

Windows

Attachments

You should attach a save file.

if it's what I think it is, this is a limitation of how the game does the truck pathing. what's happening is that you only have 3 designations wide bridge there -- so 3 trucks will reserve the 3 reachable designations to dump there, meaning that the other trucks will have to find another designation to reserve their dumping to, but if others aren't reachable, it'll give you the error you see. there's no easy fix other than to dump wider or --

what I do, is belt the rock over to a bucket nearby (so they are less likely to try and drive a long distance) to the location I want it dumped and have a few trucks assigned to the bucket set to empty. what you want to do is try and minimise the travel time, cause they reserve the dump spot when they pick up the cargo, not when they get near to the destination.

speaking of which -- it'd be cool if they reserved their dump site only when they get close to the destination 😄

Yes, it is exactly as @kennyb mentioned. The dumping designations are reserved by other trucks that are on their way. This is expected behavior.