(Visual Average Speed Computer And Recorder
) is a semi-automated technique for determining the speed of a moving vehicle. It is used by police
officers to catch speeders, mainly in jurisductions where RADAR
are illegal, or to prevent detection by those with radar detectors
. A VASCAR unit couples a stopwatch with a simple computer. An operator records the moment that a vehicle passes two fixed objects (such as a white circle or square painted on the carriageway) that are a known distance apart - a speed calculation is done by dividing the distance between the two markers by the time the target vehicle takes to travel between them.
This also allows determination of vehicle speeds by aerial platforms, such as helicopters, making it easier to make a conviction.