Vascar is frequently conducted from aircraft. When you see the broad, white, stripes painted across your lane, you should recognize you are entering a VASCAR enforcement zone. If aircraft fly this zone, they are timing vehicles as the vehicle passes through the timing markers.
A Vascar computer. These are not rocket science products. Esssentially, they are a fancy stop watch with some added features to calculate the speed for the officer. The more bells and whistles the manufacturer can add, the more tax money the police can spend for a Vascar product, which is nothing more than stop watch.
VASCAR (Visual Average Speed Computer And Recorder) is a technology for determining the speed of a moving vehicle. Unlike laser guns and radar guns, this type of police speed trap is typically invisible to you. You don't see police, as they may be flying above you, or perhpas the road simply has pressure markers or laser beams across the highwy. VASCAR is used by police to catch speeders in jurisductions where RADAR and/or LIDAR are illegal, or to prevent detection of the police by those with radar detectors.
A VASCAR unit couples a stopwatch with a simple computer. Speed calculation is done by dividing the distance between two markers by the time the target vehicle takes to travel between the markers. A typical Vascar product used in a police car is the size of a small radio, may be mounted in the police car, motorcycle or airplane. When the suspected speeder's car passes a point determined by the officer he flips a switch. When the suspect's car passes another point, the officer turns the switch off. Elapsed time is automatically recorded by the computer. It could be a totally automated system, connected to a photo camera.
The speed of a vehicle being watched is measured by simply turning on a switch when crossing a pre-determined highway marker; and switching off as the vehicle crosses the second marker. The police car is used only to measure distance and its speed is not a factor in determining whether or not the suspect is speeding. But Vascar can also be a simple stopwatch and calculator. Speed = Distance / Time.
Distance is the measured line between two markers on the highway. You have seen these markers: a horizontal white bar painted about halfway across the highway lane. The second bar is a "known", distance further, perhaps 100 yards or 100 Meters. At 60mph, it takes precisely 60 seconds to drive one mile. If there are two markers on the highway, exactly 352 feet distance, it takes 4 seconds to cross this distance. If you are traveling faster than 60mph, then the time will be less than 4 seconds. A stop watch is easy to start and stop, thus it is easy to measure the speed of a vehicle Many cities use aircraft, as 99.99% of all drivers will never see an airplane off in the distance to the left or right or behind the target speeder.
Using a stopwatch it is easy to "start" and "stop" the watch, look for a time less than the posted speed limit time. A quick radio call to a sitting police car down the highway tells the highway patrol car which car to pull over and what speed to write the ticket. There is no way to defeat Vascar, whether the officer is using a Vascar computer, or a simple stop watch.