RoR currently only has a simple waypoint AI. The terrain has to be setup for it, and as of now the only maps to feature it are Bajarama V2 and F1 TestTrack.
To use it, just select the AI version and a vehicle will spawn, it'll begin driving once its activated/entered. Both maps use the MeanMachine pack: https://forum.rigsofrods.org/resources/meanmachine-pack.261/