umm i was driving on I-10 one night going to another state and i was doing about 115 to 120 just pacing that speed because i didnt see no other cars and all of a sudden i saw a car behind me about a good mile and i started speeding up to like 130, then about for a good mile i started slowing down to about 110 then all of a sudden bam i realize it was a state trooper, then he speed up and got behind me with the blue and red lights, so according to your question, i would say if you are driving that fast and you see lights behind and you cant tell if its a cop or not, just keep going and dont slow down.......lol