In your driving session, click the monitor icon on the Display Menu, aka the monitor icon.
Click on Track Path Display.
The option you want is at the top: No display on focus train located at the top.
I ran into this a short time ago myself and spent a lot of time figuring out what I clicked on.
Since that time, I find it useful for testing sessions to ensure the drivers can get to various points I intended them to go to without going on a roundabout route.