With all this happening half a mile ahead, you have completely overlooked... braking? Changing in to another of the three, four, five etc. lanes a motorway may have? You are contriving scenarios increasingly more elaborate and unlikely, and continue to remove the several options for avoiding the accident people are providing, like the most obvious - stopping - which a car capable of 180 MPH will be able to do in a third of a mile, if not a quarter of mile.
Oh, sure, if the absolutely unbelievable happens an airship might crash in to the motorway half a mile ahead of me, my brakes simultaneously fail, and I'll crash in to it. Yup, you have me there ross, I couldn't possible get out of that one!
I have a funny feeling this 'scenario' is going to start occuring closer than half a mile now..
When did I say the car spun out half a mile ahead of you?