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· There are three main methods police use to nab speeders. The most common is radar, followed closely by laser. Third is by pacing. Radar can be used either with the police car moving or stationary. Laser can only be used when stationary. The officer either aims the hand held unit out of the window or it is set up on a tripod by the side of the road. An officer can also use it hand held when standing by the roadside.
The main difference between radar and laser is the beam. A radar beam transmits down the road in a conical shape. Imagine a flashlight beam. The further away from the source (the antenna), the beam gets the wider it becomes. The width of the beam is 15% of its length. As an example, a radar beam that stretches down the road for 1,000 feet would be 150 feet wide. This would obviously cover several lanes of highway, in both directions. An officer has to be very sure of his target vehicle.
Radar can also be used from inside a police car while it is moving. One of the more common models has two antennas, one facing out the front windshield and the other out the rear window. A flip of a switch activates one or the other. The front antenna also measures the speed of the police vehicle by the use of a second beam inside the main one and bounces signals off the road. The patrol car’s speed is displayed in a separate window from the target speed on the control box in front of the officer. He is supposed to verify the car’s speedometer reading with that of the patrol car’s radar speed reading.
There are also switches that will change the target acquisition from vehicles going in the same direction as the police car to those travelling the opposite way. Another switch will allow the radar to be used while the police car is stopped by the side of the road targeting vehicles in either direction.
A Laser beam on the other hand is much more focused. At that same 1,000 feet away, a Laser beam would only be about 4 to 6 feet wide, barely the width of a car. A Laser unit has either a sighting scope or a heads up display (HUD), where the operator sees a red dot. By simply placing that red dot on the frontal area of a vehicle, usually the licence plate or headlight a speed reading can be obtained and there should be no confusion as to which vehicle was targeted.
There is a fourth method, used mostly during the summer months, in cottage country and that is by the use of a spotter plane with an observer police officer using a small computer calculating the speed by dividing distance over the time a vehicle takes to pass between road markings that are ¼ mile, or 1,320 feet apart. This will provide an average speed over that distance. Intercept officers are positioned down the road and receive the information by radio from the officer in the plane.
Pacing is where, using the police car’s speedometer, a police officer follows a target vehicle at a constant distance behind over a distance of at least 250m. The speed may vary of course, depending on the actions of the target vehicle.