I use an advanced radar unit that will give an accurate reading off a bicycle rider at some distance. The modern radar guns are "instant" on, so a detector can't see them until we get a speed measurement. So that I can say in court that I was measuring the vehicle that I claim, I generally will target vehicles in the lead of a group or with enough separation between them that I am assured of an accurate measurement.
The unit we are issued is battery powered so we can use it away from the vehicle and then radio a partner vehicle to make the stop. I don't even bother stopping a vehicle to make contact (check ID, insurance, warrants) unless the vehicle is 15+ mph over posted. In Arizona 20+ mph over posted is criminal, so I focus on these.
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