Visual Average Speed Computer and Recorder or VASCAR is a type of system used to determine the speed of a moving vehicle. Developed in the mid-1960's, VASCAR has been used by many traffic enforcement agencies as an alternative to radar and laser guns to avoid detection by radar detectors and catch speeders.
The concept of VASCAR is relatively simple. Visual markers are placed on or near a roadway and spaced a specific distance apart from one another. Using a computer and/or stopwatch, an officer "clocks" a vehicle crossing the marker zone from the moment it passes the first marker to the moment it passes the last. Using the formula Speed = Distance/Time the officer can calculate the speed of the vehicle based on the time it took that vehicle to travel the distance between the markers.
VASCAR can be used by traffic enforcement officers while they are moving or while parked, and there are several methods used for each scenario. When in motion, the officer can clock a vehicle while following it, when approaching it from the opposite direction or when the vehicle is following the officer from behind. When stationary, the officer can either be parked adjacent to the road, or at an angle, at ground level or from above the road, such as on an overpass. Some states, such as Florida and Iowa, often use aircraft for VASCAR, or a combination of both ground and air assets.
While not new, VASCAR is still actively used. It is commonly used by traffic enforcement agencies as an alternative to radar and laser in order to avoid detection by radar detectors. In some states, it is the preferred system for speed enforcement. If you travel in or across these areas, you need to be informed about VASCAR and alert to its possible use.
To learn more about VASCAR, download this Analysis of VASCAR from the U.S.Department of Transportation and the National Highway Traffic Safety Administration.