VASCAR

VASCAR (Visual Average Speed Computer And Recorder) is a type of device for calculating the speed of a moving vehicle. The first VASCAR device was created in 1966 by Arthur Marshall. It is used by police officers to enforce speed limits, and may be preferred where radar or lidar is illegal, such as some jurisdictions in Pennsylvania, 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 road) that are a known distance apart. The vehicle's average speed is then calculated by dividing the distance by the time. By applying the mean value theorem, the operator can deduce that the vehicle's speed must be at least equal to its average speed at some time between the measurements.

VASCAR can be used from a moving or stationary patrol vehicle, and the target vehicle may be travelling in the same direction, in front of or behind the officer. It can be approaching from the front, or even on an intersecting highway. This technique can also be used to determine a vehicle's speed from helicopters and other aerial platforms, making it easier to secure a conviction.

A 1991 study by the National Highway Traffic Safety Administration found that VASCAR-plus units produced errors of less than 2 mph if used correctly.

VASCAR is known to be used where radar or LIDAR is illegal, such as some jurisdictions in Pennsylvania. Many police vehicles in the United Kingdom are fitted with a device, especially those used for traffic enforcement. The system is also used by airborne units - in some remote locations of the United States airborne speed enforcement is employed regularly.

VASCAR was invented by Arthur Marshall, a real-estate investor living in Richmond, Virginia in 1966. He was inspired to create the device after watching a police car driving dangerously trying to pace a speeder. The original version of the device was entirely mechanical, using a governed motor and a gear system to move a pointer to the correct speed value. Subsequent versions used a microprocessor to perform the speed calculations. By 1968, the device was in use in North Carolina,Indiana, Kentucky, and New York. In 1971, Marshall formed a company, Traffic Safety Systems, Inc., to market the device. After his death, Traffic Safety Systems was purchased by Power Systems & Controls, Inc., which had long manufactured the devices. They continue to produce similar devices under the name VASCAR-plus.

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