I received a ticked for going 80 in a 65. I was driving about 7 car lengths behind a police officer for about 5 miles but my speed never reached above 70. On the ticket it stated my speed was clocked. The options were Radar, Clocked, Estimate! What equipment or technique do the use to "clock" your speed? Can this be action of "clocking" be done when the car is behind or in front of the police officer?