Okay, first, here is the situation:
Here we see what should be a pretty busy station. It can receive 4 different kinds of raw materials and turn them into goods. As you can see, the main trunk line that leads to this station dead-ends here. The trunk itself splits off a couple hundred tiles up the road, disseminating traffic nicely. In other words, the main trunk line can take a lot more traffic in needs be. I also plan on bumping up my car length to the max soon, which will put a whole heck of a lot more product into and out of this station. My problem isn't however, with this specific game, but how in general to include mandatory depot stops into very high volume stations. I know that maybe mandatory service stops maybe aren't 100% necessary, but I'd still like to solve this problem.
I had before used one depot with the track setup such that the trains had to stop there before moving into the station branches. One depot is far too slow and traffic would often backup as it waited to enter the depot. I had, in previous games, devised this diamond-type depot entry which allowed trains to choose the top or the bottom depot, essentially doubling my depot processing rate. It's worked okay in other games, but every now and again I run into troubles. The trouble is, as you can see in this first screenshot, that trains sometimes refuse to choose one or the other depot and instead stop at the light and wait for the train ahead of them. At first, I thought the problem lay in the fact that when the first train completely enters the depot, the light outside the depot would flash green for a second, perhaps inducing the second train to think the path was clear. I found this later to not be the problem. I tried a different configurations without luck.
You can see what a disaster this abomination is. My thinking was, hey if the station branching and presignalling works so well, why not include the depots into the mix and hope they continue to operate as planned. The problem here, I think, is that each depot entry point has an invisible signal on it, which can fool the presignal into believing a line is open when it's not. I decided it was better to not mess with the station branching as pictured in the first shot since it worked so well.
I thought I was onto something with this layout. However, I witnessed an odd behavior that really defied the notion of presignalling. It seems that trains don't "look ahead" at all, not even a little bit. In this shot, you can see a train that has passed up 3 green lights to come to a stop at the last red light. Note that the light it's stopped at was red when it entered the presignalling block and continued to be red until reached the light. I have tried several permutations of signalling at this last configuration of track, and nothing works. Oddly, about 5% of the trains entering the station will choose a depot but the last and, for a brief moment, this interchange will work as planned. I've watched for these moments and tried to figure out what was different about them that would cause them to actually work, but I can't see any difference.
Can anyone offer any insight as to how I could make this work? I understand that I could maybe try suck machinations AFTER the station, but I would probably be at risk of the same thing happening. I am looking for a completely airtight solution to satisfy my mandatory depot stop mania. Thank you.
