How is Train Priority Determined?

[bballjo]

I'm in the end game and after i made a few Billion i decided to change the cargo system from the usual point to point with dedicated lines to a hub based system, where i have a NORTH/SOUTH/CENTRAL hub on the map, with each servicing the same amount of cities and they all receive goods.

After a while i saw one of my hopper trains wouldn't move, and i didnt move for 30 mins real time, which was about 3 years game time (full speed). That train is part of a hub that has 7 platforms, and each platform services 2 routes, thats just the way it worked out.

I have a queing system that goes into the hub, with 1 track per line, and i have a queing system that goes out of the hub, with 1 track per platform, just to move trains out faster. They all eventually go onto a shared single track.

I had the train reverse numerous times and started placing more random signals and relayed track...at no point did the train move past its own line, meaning it was never 'allowed' to get onto the main track...DOES ANYONE KNOW WHY?

I assumed trains worked on a queue type system, with mostly first-in-first-out, but it doesnt seem to be that way. The only other reason i can think of is profitability, but although this wouldnt be my main money maker by far, it should still be able to make some money...it just seems very strange.

I spend some time observing the other trains on the other platforms, and was able to confirm that train priority its most definetly not determined by a queue. If anyone has any ideas pleast share.

PS: Hub system with Consist trains 'works' but is not very profitable IMHO.

EDIT: This received a lot more comments than i expected in this time...i just went into the game to get some screenshots and found that the train that i described above got release, but now other trains are stuck again. After waiting for a little bit the best i could see it that its a Last-In-First-Out system, which seems really odd.
Since this is still 'an issue' ill post the screenshots so you may get a better idea of what i described above:

Configuration: All enter on one side, and leave on the other. Nobody backtracks and everything has 1 way signals.
https://steamuserimages-a.akamaihd.net/ugc/771738332926261336/755BE3FD0983C59DC0B94A4A9E5ADCDBCEDB89CB/

Leaving the Station: Queueing for exiting the station to get back onto the mainline. The mainline exit is 1 track with more queuing one way signals.
https://steamuserimages-a.akamaihd.net/ugc/771738332926263364/B4B58B9A86561D83BD154AFFEAD7A4B21EBA6BBB/

[Vimpster]

I can't really help you out in your particular issue as your description of the circumstances does not make any sense to me. But beyond that I can say that the priority that is used when it comes to signals is first come first serve for the most part.

[canophone]

Trains will only move if the path in front to the next signal is 100% clear. There isn't any built-in priority for that. If another train has already reserved a path the train waiting at a signal wants to use at any point, the train waiting at the signal won't move. If you want a specific train to move, you must manually stop the train that is in the reserved path (as long as it won't be in the path of the train you want to move).

[CashonWheels]

It not FCFS when you have 6 trains waiting on one signal. The first 'free' train is the one that leaves, regardless of arrival time. I'm always using hubs and I used to have the same issue. I counted one time in a game where one train was ready leave but never it got clearance to leave for a full hour. meanwhile a 'local' that serves the nearest town came in & out four times. That is an extreme case due to too many trains trying to funnel onto too little track. Most of this is solved by adding track further down the main line.

The amount, size, and placement of hubs is also a factor. Just placing 3 bigs evenly spaced apart sounds predetermined.

every map is different.


I had a map where I placed 4 mega hubs and 2 medium hubs.
another 1 Mega, 2 large and 6 medium.
and another with 2 medium and every other cargo station was a town and or factory . This was due to the shape of the landscape. That map mostly was a relay system.

[SBGaming]

I had a situation where I had some trains entering a main track from a depot, and was waiting at a signal. A train that was passing through the junction on the main track was given priority over the new train entering, but as it was passing through the junction, a second train approached from the opposite direction and because it's path was clear, it was allowed to go, requiring the trains coming from the depot to have to wait longer. While the second train on the main track was passing through the junction, a third train on the main track going the same direction as the first was cleared to go through and took priority, leaving the train waiting to enter to have to keep waiting. Due to how busy it was, there was almost always a train in the junction that prevented the train wanting to enter to have to keep waiting, and this was a section of track where four different lines utilize what amounts to a two track section.

Basically if a train is prevented from passing a signal because the path is in use, other trains can be given the go ahead if their path is clear. This might generally be desired behavior, except when the activity on a particular set of track would result in a train waiting what would effectively be forever.

[Kniff]

I guess every train has his own tick, checking what to do next and there is no general dispatcher and the train which is checking its path doesn't care about anything else but if his path is free or not.

It could be worth to try out to save and reload the game if anything changed or if the order of ticks is the same again then.