Does anybody know the range on these?

as was doing 85 on dual carrigeway trying to get home to watch fottie!

but got a flash from oppsite side of road then slammed on brakes to do 60 then saw a white van with black tinted windows and POLICE on the side and then drove past @ 60

any comments welcome as i cant really afford 3points as im only in my 2nd yr of driving!

Tiller_mistral