So here's the scenario. I'm at a red light in the leftmost straight-going lane, about 6-8 cars back from the light. Tractor-trailer is in left turn only lane, he's first in line at the light. Light turns green for both straight and left turn.

Tractor trailer begins turning left, straight going lanes start moving. But the tractor trailer isn't turning left, he's making a super-tight U-turn.

As I approach the rear end of his trailer, the driver side corner of the trailer actually starts pivoting out into the leftmost straight lane of travel because he's turning so tight that the corner is going backward not forward.

I swerve and miss him and luckily no one was close enough to my right side, so it all turned out OK. But who would have been at fault if I had hit him? He was making a U-turn and effectively "reversed" the trailer corner into the straight going lane of travel by turning so tightly that one set of wheels was going forward and the other backward. Was he entering a lane of travel? Or would I have been basically rear ending him? (even though I would have basically hit the side of his trailer).

I can draw a picture if this is hard to understand.