Drive to, Drive Via, Navigate...

I am trying to get an AI train to run from the north end to the south on a double track main. I put down trackmarks to designated the path it's to follow. I can't seem to get the train to keep moving at full speed from trackmark to trackmark. It slows down as it approaches the next mark.

I've tried "drive to," "drive via," "navigate to," and navigate via." I don't know what I am doing wrong. I can get the train to stop at the stations, unload and load passengers, but not keep moving at track speed when approaching the next trackmark.

I doesn't seem to matter if the train begins on the route or is created by the portal.

This seems to be a problem with TS-19 and not something you are doing wrong.

'Drive to' and 'Navigate to' suggests to AI that the train is going to stop and do something, whereas 'Drive via' and 'Navigate via' suggests the train is going further, however when you reach that 'via' command AI has to be able to locate and plot a route to that next destination/command. The more complicated that route is the more AI struggles and when AI struggles trains slow and stop. Such confusion can be caused by distance, junctions, stations and any other distraction along the route where AI might be required to make a decision.

To help things along, track markers, direction indicators and their placement all helps inform AI of your intentions. Speed indicators in association with 'Max speed' commands remind AI what limits are and together with points set to priority routes all help keep things moving.

To experiment, move track markers before or after junctions, away from signals, and perhaps remove any which are in the middle of nowhere. Watch what signals are doing, anything other that green (route clear) causes trains to slow before you get anywhere near them.

I have quite a busy 100 mile mixed traffic through route with multiple junctions use TRS19 without any issues other than the odd passenger trains being held up by a slower good train so I'm not sure TRS19 isn't inherently faulty although AI is very much a mystery. Peter

Use 'Drive Via...' for the minimum impact on speed. If the section of track is rated for 60 MPH (~102 km/h) then a through-train operated by an AI driver drops at most about 3-5 MPH/ 5-8Km per hour momentarily if it is already at rated speed and there are no obstructions ahead.
Think this may in fact be influenced by the speed of your rig's CPU and how AI serial command scripting operates. In earlier T:ANE days, there was little perceptible speed-dropoff using 'Drive Via...' but there have been some scripting changes made in the past couple of years that induce the slight drop-off in current speed.
Use Drive to... when you want the consist to slow to a near-stop or if the next driver command is to 'Wait X minutes/ seconds', or to 'Load/ Unload' (at an interactive industry).
Track mark placement/ locations are important as wilts747 suggests above. Use as few track marks as is absolutely necessary, but sufficient to ensure AI drivers stick to the path you've ordained.
I'd recommend that the 'Navigate to...' command should only ever be issued when the consist has travelled very close to its destination stop-over (i.e. a station or industry pickup or dropoff point) and when there's no alternative path for the AI to consider.
Example Driver Command sequence might thus be: Drive via 'Maintrunk East - Southbound', Drive to 'Port 2', Wait 10 seconds, Navigate to Port Kea, Coal Dropoff, Unload, Drive Via Port Exit, etc...

Here's a good explanation on what the difference is between the two commands:

https://forums.auran.com/trainz/showthread.php?33716-Driver-AI-what-are-they-thinking

Specifically in this link here:

https://forums.auran.com/trainz/sho...AI-what-are-they-thinking&p=367836#post367836

From the old manual:

Drive To Command

Drivers will choose the shortest valid route to their destination without taking into account current positioning of other traffic. If other traffic is on the required line when the Driver arrives to a certain block, the Driver will wait for the traffic to move rather than navigating around the obstruction.


Navigate To

Drivers will choose the shortest valid route to their destination along clear blocks. If other traffic is on the required line when the Driver arrives, the Driver will navigate around the obstruction and re-path to the destination.

There is a slight pause but not like there used to be. Use the Navigate to command for out in the middle of nowhere, but use the Drive to command when there's a lot of congestion such as in and around yards, stations, and terminals.