If the worst happened and there was a quiet 3 carriage way road below
I have heard it argued that it doesn't really matter whether the road is quiet.
The thinking is that in the case of a motorway, touchdown speeds will be similar to vehicle speeds. As you swoop down to land, traffic approaching behind you (as well as being somewhat surprised) will naturally brake, whilst traffic already in front will in any event be accelerating away from you, either oblivious to your presence, or with alarm at the sight in their rear view mirror.