Ever wonder why there are two white lines spaced about 1/4 of a mile apart on the Interstate highways? Now you know why. They use the lines for the VASCAR in the airplane. All they need is the time and distance. With the white lines, they have the distance. Then they measure the time it takes to travel between the two lines.....now they have your speed. The troopers on the ground are given, via 154.695 Mhz., the speed and description of the speeding vehicles (Unless your very close, you cannot hear the ground trooper). The trooper pulls out onto the Interstate. The spotter in the airplane then tells the ground trooper when the vehicle is next to the ground trooper. The airplane will then verify that the trooper is stopping the correct vehicle. The ground trooper provides the spotter the tag information. The spotter then gives the ground trooper the confirmed speed and time. The spotter maintains a log of the stops. The ground trooper writes the ticket. Both troopers go to court to testify. Instant conviction.