Just a small addition to this for vehicle behaviour, apologies if its already mentioned, I did scan the posts..
When a vehicle gets stuck, or is attempting to turn around, it clearly has trouble deciding which way to go, whereas a 3 point turn style of moving would possibly cure a few of these issues.
If the driver decides that moving forward isn't getting him anywhere, which occasionally happens, then he will full lock in one direction, reverse, straighten his wheels then full lock in the same direction, thus driving straight back to where he was, repetitively.
If he was to reverse (full locked in one direction) then drive straight or full lock in the opposite direction, the majority of stuck vehicle cases would be reduced.
Also, why on earth do the AI continue to struggle forward when they have no tyres whatsoever :)