The cop sees a smudge of grease covering a tag and says it would keep the readers from seeing the real tag number. He then calls in and confirms the guy has only paid 3 tolls over the last 3 months. Since data takes little space, I guess they keep the record of who is where indefinitely. The one guy had a tail gate down hauling ladders and they claimed he had no need to have the gate down for the shorter ladders. I guess if he had a few feet longer pipe or board in the back he would have a get out of tolls pass. I notice Florida has a tag on front and back, many states are rear plates only.