Why does my AI train suddenly slow?

[bwfeldsee]

I know that AI trains can be stubborn beasts but I can usually get them to go where I want (eventually) by giving them enough "drive via" instructions. However I haven't yet understood why they might suddenly slow down then speed up again for no apparent good reason.


On my route I have nice stretch of double track main line for 70 mph running with a station part way along a section of dead straight track. One of my sessions involves driving a local train which stops at this station for a minute or so. Whilst there, an express comes along in the other direction doing 70. When it reaches the station (which is one of its "drive via" marks) it suddenly slows to around 20, thinks about it, then speeds up again. The only other bits of info I can give are that its "drive via" instructions for the rest of its journey are correct but there is a trailing crossover at the far end of this station - nothing to do with this particular session but is it confused by this?


I have noticed the same thing in other places with various trains and wondered if there is something I should avoid when setting up an AI train.


Any guidance gratefully received.
Regards

Alan

 

[sniper297]

Fear of flaming death?

AI engineers are overcautious at times, best way is to use speed limits sparingly and signals liberally.

Standard way to signal a crossover, double head on facing points, single head just before the trailing points. if the switch is set for the through route the single head on the trailing point should be green. (This is a US route with the controlling signals on the right side of the track, you being a Brit you should imagine that picture with the signals on the other side) If the switch is set for the diverge by default, edit the session in surveyor;

Select the track object tool, then the junction direction tool, click on the switch to throw it straight. To make that stick;

Use Save instead of Save As, overwrite the route AND the session. Set all the mainline switches for the mainline by default and the AI will have to find something else to be paranoid about.

 

[bwfeldsee]

Very many thanks for this very helpful reply which will come in useful for the future - I hadn't appreciated the importance of having all the signals present and correct. Oddly, it didn't provide the answer on this occasion but, after some experimentation, I discoverd that removing the "drive via" instruction at this particular station did the job. Even more curious is that "drive via" instructions at other stations didn't cause the same problem and I tend to use them a lot to ensure that AI trains go through the correct tracks in the station. All part of the learning curve I guess. Thanks again.
Alan

 

[sniper297]

Placing a trackmark at or near the station and using drive via trackmark if you want the train to bypass the station would probably work better. I suspect if you're using drive via station (name) platform 1 or something, it sees that as an interactive industry that it might need to interact with, therefore slows down anticipating the load passengers command coming next, then returns to track speed when it sees the next command is NOT load passengers. Not 100% sure, but I think the AI only reads one command at a time, but assumes any named interactive industry destination (which includes passenger platforms) will be followed by a load/unload command.

 

[bwfeldsee]

That's an intersting point which hadn't occurred to me. The trackmark is indeed half way along the platform and has the same name as the station followed by the track (platform) number. These AI drivers are fiendishly clever when it suits them and dumb when it doesn't!
Thanks again.
Alan

 

[Dermmy]

...Even more curious is that "drive via" instructions at other stations didn't cause the same problem..

The trackmark ~~ has the same name as the station followed by the track (platform) number.

Just to add to Sniper's point, are you absolutely certain that the 'Drive Via' which is causing the problem does in fact reference the trackmark? If the TM has the same name as the passenger platform the 'Drive/Nav via/to' menus are set up in a way that makes it is very easy to accidentally reference the platform....

 

[sniper297]

My first impression of Trainz AI was that it's intelligent but psychotic.

http://www.youtube.com/watch?v=xJb_8UywoRA

Using Drive instead of Navigate is like giving it Prozac, no idea why Navigate is enabled by default and Drive is disabled by default.

 

[Dermmy]

... no idea why Navigate is enabled by default and Drive is disabled by default.

'Cause it's 10,000 times better! Under 'Nav Via' the action of an AI train is pretty much 100% predictable. If the train goes the 'wrong' way it's pure and simple operator error - fix the route! I haven't used 'Drive Via' once since the improved command got written. I admit I jacked up at the time, mostly because the AI performance was different than the old command, but once you get your head around 'Nav Via' it is sweet indeed....

 

[sniper297]

Hmmm, I get the complete opposite - with drive to or via trackmark two trains approach a single track section in an opposing meet, one stops and waits for the other to pass, then goes on to the next trackmark. With navigate to or via the one that has to stop can't wait a couple minutes at the red signal, he wants to back up 10 miles, divert onto a branch line, cross over to the scenic route and go the wrong way around a big circle for two hours before finally getting to the trackmark that was originally less than half a mile and five minutes away if he had just waited. Then he's facing the wrong direction and completes the rest of his instructions backing up. Possibly the difference is complex or circular routes with several alternative ways to get to the same destination, with a simpler point to point route navigate works fine because they don't have so many alternate choices.

 

[bwfeldsee]

The learning curve just got a whole lot steeper! I'm really enjoying this discussion between Dermmy and Sniper but confess to being out of my depth. Firstly, just to answer Dermmy's question to me, the trackmark and station do have slightly different names in that only the trackmark has the word "track". So I was definitely telling the driver to drive via the trackmark.
On the wider issue of "drive via" or "navigate via", I've noticed discussion on this topic previously in the forum but, as you say, it defaults on "drive via" and that's all I am offered. How would I activate the "navigate via" or indeed can I? I am working in TRS 2006.
Meanwhile, my session is working fine with the one "drive via" command removed. I was definitely worried that the driver was going to seize the opportunity to go wrong road in the absence of the command but he must have been asleep!
Alan

 

[sniper297]

I couldn't tell you that, I've never seen 2006 except for the demo long ago. Again tho, check that the switches are set for the main by default, if any switch is set the wrong way the AI will slow to examine possible paths to the next marker, if it's already set the right way it will continue at track speed. They do also slow down way way way in advance for yellows or lower speed limits, rather than fiddling with all the complicated work arounds for that I just increase speed limits and make sure switches are set for the main when I want them to run faster.

Old argument about Artificial Ignorance in railworks keeps flaring up from time to time,

http://www.trainsim.com/vbts/showthread.php?310321-What-Is-Wrong-With-AI-Plenty-BUT

However many problems there are with Trainz AI traffic, it still beats the pants off the other two.

http://www.trainsim.com/vbts/showthread.php?310322-What-is-RIGHT-with-Trainz

 

[Dermmy]

it defaults on "drive via" and that's all I am offered. How would I activate the "navigate via" or indeed can I?

Sorry Alan, I missed that you are in TRS06.

'Drive Via' was the default (only?) option in that version. IIRC there was an 04/06 version of 'Nav Via' on the DLS but whether that was the same as the new built-in 'Nav via' I do not know. The 'Nav Via/To' commands Snipe and I am comparing are the new default commands in TS10 and later. In TRS06 I was using the default 'Drive Via/To' commands in sessions, same as you are using.

The other issue that could be causing a slow-down is a signal that is red as the train approaches, but turns green as the train gets closer. I have occassionally had spots where a sig turns green/red/green as the AI sorts out the junctions. It would be worth hanging around a couple of sigs farther down the line in Camera View '4' as the train approaches the troublesome station...

Andy

 

[JohnnyC1]

I've had a couple of instances where that has occurred, consists slowing, all turnouts alined to the flow of traffic, signals placed as they should, still the train slowed. I did a map view of the track and found there was a gap in the rails on the map but not in surveyor or drive, removing the track and relaying fixed the slow down. The other slow order was fixed by placing a invisible permissive signal between the visible signals.

John

 

[bwfeldsee]

It's very kind of you all to be sending the helpful comments - much appreciated. In reply to John, I checked the track map after I saw this message but that was OK. I was very tempted at this point to leave well alone as I had accidentally solved the problem by removing that one command to drive via the station trackmark.
But then I thought that would be evading the issue and I really wanted to understand it. I went back to Sniper's very first comment about the signals and had another good look at my track plan. Then I remembered that, a couple of weeks ago, I had moved that particular trackmark further back down the platform as AI trains that were due to stop were overshooting the platform. It was now the wrong side of an inadequately signalled facing crossover. Moving it a few yards to the other side again seems to have done the job.
So thanks again.
Alan

 

[Tyrennis]

I have this problem alot. Even used invisible speed markers. Sometimes it works, other times it doesn't. Also watch for yellow Signals as they make the train slow to ½ speed.