The very first traffic enforcement cameras date back to the turn of the 20th century and more than 100 years on they still manage to strike fear into most motorists. The same basic principles that were used back then are still used to this day. The camera will basically take two photos between two measured points on a section of road.

These initial cameras were, of course, very primitive in nature and the first real traffic cameras as we know them today came into force during the 1960’s. In fact, these cameras were still being used until the early 1990s until the era of digital technology was among us. There are various types of speed camera, but in this article we will look specifically at mobile cameras.

Mobile Cameras

Honestly Officer I Wasn't Speeding - A Quick Guide To Police Mobile Cameras

Image License: Creative Commons image source

Mobile cameras are typically referred to as radars and are usually found on a police vehicle. They can be hand-held, concealed or tripod mounted. They are known to come in a wide variety of shapes and sizes. Due to the built-in detection technology it makes no difference whether the officer is moving or stationary, they are still able to accurately record the speed of a motorist. This is also true even if the camera carrier is moving against the flow of traffic.

The Doppler Effect

Honestly Officer I Wasn't Speeding - A Quick Guide To Police Mobile Camera

Image License: Creative Commons image source

The camera will emit a light beam, such as that used in laser technology, towards an oncoming vehicle. At a range of approximately 800 metres it takes no more than 0.3 to 0.7 seconds to register a specific target. Once the target has been locked the “Doppler Effect” comes into action. The Doppler Effect can best be described as follows:

The camera will send out laser beams at specified and intermittent frequencies across the road. As soon as a car enters within its field the radar will be reflected, thus causing the beam to change frequency. The actual degree to which the frequency changes (either increases or decreases) will depend on the speed at which the vehicle is travelling. A mobile camera will also reveal the direction in which a vehicle is travelling – the vehicle will be coming towards the camera if the frequency increases and it will decrease if the vehicle is moving away from the camera.

How Does a Mobile Camera Determine the Speed at Which a Vehicle is Travelling?

As mentioned, the increase or decrease in frequency will determine the speed of a vehicle. The beams are typically directed at an angle of 20 degrees in comparison to the road. The radar will use trigonometry (yes, it does come in useful for something) to calculate the slant angle, which will then help it to calculate the actual speed at which a vehicle is travelling.

A Quick Guide To Police Mobile Cameras

Image License: Creative Commons image source

Mobile cameras are simply one form of speed control on our roads. Many of you will be far more familiar with fixed speed cameras, typically mounted on poles or hanging on bridges or overpasses. There are also average speed cameras, which unlike other speed cameras do not make use of lasers, GPS or beams. In fact, average speed cameras do not make use of any real modern technology, but simply rely on camera photos and a little basic arithmetic.

This article was submitted by Jack Ramon; he works for Melbourne criminal lawyers and he is dedicated to his work. He often indulges in writing about law and related issues in order to help readers and create awareness among them.