The road less travelled

Snow started as I was getting dressed, and the cold overnight meant that for once it was settling. So I took the long way around on the main roads to work.

It was obvious from the difference between the two lanes on the radial A road quite how much more traffic goes into Cambridge than comes out; the inbound lane was almost dry; the outbound white with tracks, so slow going.

Slower yet when White Van Man arrives behind me and stays about a length away, so I keep my speed down to allow for his stopping distance as well as my own.

Which part of “Keep your <expletive deleted> distance!” don't they get?