The AI seems kind of "dumb" right now. In Flee mode, it heads straight towards a barrier and crashes into it. However, I've seen videos with perfect AI. I'm using official cars and terrains, so what's happening?
The AI currently is much different than it used to be. It's set up now so the AI can automatically drive around a set course on maps, not so it can follow or run away from the player. I've heard that the follow and flee features are going to be added back at some point but for now the devs are focusing on making them more intelligent. There is a mod though that can restore these features for the time being if you're interested. http://www.beamng.com/threads/15527-AI-Replacement
I'm not quite sure what's going on. The 'Flee' mode seems to be working pretty well on my end, even on custom maps. Does the 'random' mode work well at all? As corrections to the above, the 'flee' mode currently does exist for the new AI, albeit not flawlessly. 'Chase' has yet to be reintroduced. Installing the AI Replacement mod will add chase back, but both chase- and flee-possessed vehicles will run blindly into obstacles. Push comes to shove, I might advise deleting ai.lua under Steam>steamapps>common>BeamNG.Drive>lua>vehicle, and running an integrity check by way of Steam.
AI flee works surprisingly well for me, to the point where it's actually fun and funny. I like how the fleeing vehicle will drive to what approximates a "speed limit" but when I get within a certain distance it will start driving like a madman to get away, still being mindful of sharp turns.
That's strange... The AI is probably corrupted. It seems that push has come to shove. This is what I would recommend.