Dave,
You can also use direction markers to force drivers to take a specific siding or use track marks.
By default, the AI will want to take the shortest route between points and for some reason favor going left, probably due to the program coming from Australia since they are a left-side driving country. To direct the AI to take specific tracks, you use direction markers. The alternative is to use track marks which in this instance will work as well.
The Direction Markers and Track Markers, found under the triggers and markers tab on the Track-menu in Surveyor, work as one-way signs. You place down two of them so that the points point in the direction you want to go just a bit passed the frogs on the switch.
When your AI drives, they will take the appropriate track when they encounter the direction marker.
For a bit more flexibility, you can use track markers. These are bit more complex to setup, but not so bad. You place a track marker in the middle of the siding, not near the end. When you place a track marker, the properties window opens up and you can then name the marker to whatever you want.
When setting up the driver schedule, you choose Navigate via track marker. A window opens up and you scroll or type the name and then select the one that highlights.
When the AI driver runs, the driver will now choose that track marker and head down that track.
The reason for placing the marker in the middle of the track is because the AI will cheat. Trust me if they can, they will cheat their way through the route. If you were to place the track mark too close to the switch, the AI driver will navigate to that marker, backup and then go down the wrong track anyway! If you place the marker further along the way, they're too far into the route to backup, and will continue on their way to the end.
