Edit, more: tree down across the road, truck can't drive over it. Get out and wrap a chain around it to move it. Busted axle, how will it fix that? Flat tire? Mechanic used distilled water like a dumbass and it froze. Road sign was taken out by an accident, guardrail is missing, hope you arent using those to determine how to keep on track.
Driving on icy gravel, that's just a physics simulation, with no opponents.
The hard part of self-driving is vision, with hard constraints on real-time and power supply — how long that takes (especially given the enormous pile of scenarios we don't think about when trying to list them but do know how to deal with when we encounter them), I don't want to guess, as I think it could be anywhere from negative 6 months to positive 16 years.