Average Speed Computers
Average speed computers are used to identify drivers who exceed the speed limit. The full name of this method is VASCAR, which stands for Visual Average Speed Computer and Recorder.
VASCAR is a speed-measuring computer that records the time it takes for a vehicle to cover a certain distance. This allows the object’s average speed to be calculated by dividing the distance traveled by the travel time. The unit is attached to nearly all road policing vehicles, including airplanes and helicopters, and can be used while the police vehicle is stationary or being driven.
VASCAR differs from radar devices in that it is used to measure average speed over a specified distance, as opposed to measuring maximum speed. The advantage of these units is that they do not require the use of electromagnetic waves to determine a vehicle’s speed. This means that radar detectors, which some people install in their cars to warn them that police are in the area looking for speeders, cannot detect the device.
The use of average speed computers is similar to a stopwatch, which was the very first method developed to track the speed of objects. But unlike a stopwatch, VASCAR makes use of a distance data feed from a moving police car that helps measure speed on the move.
To measure speed with this combined technology, police officers do not need to travel at the same speed or behind the target vehicle, such as with the “pacing method.” The police car does not even have to be traveling in the same direction as the speeding car.
The speed of a moving vehicle is determined through a simple calculation. The distance between two markers that are painted on the road is divided by the time the target vehicle takes to travel between each marker.
VASCAR devices have two sets of switches. One set measures the target vehicle’s speed, and the other measures the police car’s speed. By flipping the switch, the police officer can measure the time it takes for a car to travel between the markers and the distance between the same two markers when the police car travels between them.
The first switch is turned on when the speeding car passes the first road marker. When the police car passes the same marker, the distance recorder is switched on and begins its measurements.
As the car crosses the second marker, the timer is switched off, and the distance recorder remains on until the police car passes the second marker as well. The total time is automatically recorded by the computer.
With all of these measurements, an accurate calculation can be made to determine the speed of the vehicle. If it can be established that the vehicle was in fact exceeding the speed limit, the police officer makes a call to another police unit down the road to tell him who to pull over and what speed to write on the ticket.