Starting to work on sessions

Tried setting up a session sand box - meh...

I thought that before I tried setting up sessions on a 100 mile route I should test out my knowledge of session building.

Either session building is really confusing, or I'm trying to do something that's impossible in Trainz, or I'm clueless...

_s___s_ _s____s_

s - single head signal
z - single head signal for both directions
S - double head signal

The idea:

1) Single track mainline
2) Bidirectional trains
3) Passing sidings to allow opposing trains to pass each other
4) Portals (Portal Basic) at each end source and consume trains
5) Signals are non-permissive from the Searchlight Signal 0x family.

Each train sourced from Portal A has the following commands:
  • Navigate to trackmark TM-B
  • Navigate to trackmark TM-C
  • Navigate to trackmark TM-D
  • Navigate to PORTAL-E

Each train sourced from Portal E has the following commands:

  • navigate to trackmark TM-D
  • Navigate to trackmark TM-C
  • Navigate to trackmark TM-B
  • Navigate to PORTAL-A

In practice:
  • the first train generated says it is unable to navigate to its first track mark.
  • all other trains reverse themselves after traveling about 1/2 the length of the portal, then delete themselves.

I did not:
  • make the sidings directional, because I want trains in either direction to be able to hold the main or take the siding (prototype practice would be to assign main or siding usage depending on the situation - in TT&TO right, class, and direction determine which train takes the siding)
  • put the trackmarks on the siding(s) or corresponding main track(s), because I did not want to force the usage or siding or main for an AI train in advance of the train reaching the siding in question.

I take it I'm completely off in the weeds with this setup.

Or, I read somewhere on the forum that people are having portal problems, but I've no idea what those problems were.

I've watched the N3V youtube video for Portals, but it only using traffic in a single direction and therefor isn't a complete example of what I'd like to do.
I've watched the demos on rudysmodelrailway YouTube channel to see how he made signals operate. Again, this was a uni-directional situation. Also, he was pre-assigned siding or main at each station

Does train require a double track mainline for AI trains to pass each other in opposite directions?

Enquiring minds need to know...

Horace (more confused/frustrated than ever) Fithers

Does train require a double track mainline for AI trains to pass each other in opposite directions?

No. Passing loops on single track main lines do work but you would need to use Session Rules to manage the passing situation. Letting the AI manage the passing loop all on its own can lead to problems.

For example, you can set up session rules and driver commands so that when Train A exits a passing loop to enter the single track mainline it forces the entry signal on the far side of the next passing loop to show STOP. So if Train B is approaching the second passing loop section from the opposite direction it will be halted at the entry signal until Train A is in the loop (or on the mainline section of the loop - whichever it decided) then the entry signal is set to Automatic and Train B can navigate its way around Train A. Interlocking Towers (another level of complexity) can also do this task very nicely.

I rarely use portals and when I do I only use them to either accept or produce trains - not both in the same portal. This avoids the situation where a train is approaching the portal on its single track entry line at the same time another train is being produced from the portal.
I agree with the comment about using separate portals to produce and accept trains. Using one portal to do both functions is asking for disaster.

However, my experience has been that generally (with the emphasis on "generally") AI trainz will safely navigate a single track line with crossing loops by themselves, providing the signalling and track markers are correctly set up. The difficulty arises when a player train is introduced into the session. But there are ways of overcoming this using "Signal Link". To see how this is done, see my "Bidye Traction Railroad", here:

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One minor point I'd add. If each of those trackmarks your AI is passing through and not performing some task like a passenger stop or loading/unloading, you should really use "drive via" rather than "drive to." I have no trouble (mostly) getting an AI to load, unload and drive long distances, but I never use too many.
I keep it simpler than that... Good old KISS

I use two portals on either end so that there are no conflicts with incoming and outgoing trains because AI can get stupid.

I also use direction markers to keep AI on their appropriate sidings. It's not quite US prototypical with trains taking whatever available siding, but it keeps the Artificial Idiots from heading at each other and getting stuck, meaning all traffic heads right.

Single track is protected with two Type 04 absolute signals with the aspects facing towards the respective double track lines. The single-track line has either a 2-head Type 06 with aspects facing towards the single-track.

For the actual session, I divide the setup into divisions if the route is exceptionally long or complex, and use the Schedule Library to hold the respective division schedules.

Navigate To (industry), Navigate Via track mark and Navigate To track mark work well for open routes, but where a more direct control is needed, I will use the Drive variations.