Speed Detection of Moving Vehicles Using Doppler Effect

Topics: Radar, Doppler effect, Traffic law Pages: 9 (2868 words) Published: March 17, 2012


Although there is good road safety performance the number of people killed and injured on our roads remain unacceptably high. So the roads safety strategy was published or introduced to support the new casualty reduction targets. The road safety strategy includes all forms of invention based on the engineering, education and enforcement and recognizes that there are many different factors that lead to traffic collisions and casualties. The main reason is speed of vehicle. We use traffic lights and other traffic manager to reduce the speed. One among them is speed cameras. Speed cameras on the side of urban and rural roads, usually placed to catch transgressors of the stipulated speed limit for that road. The speed cameras are there solely to identify and prosecute those drivers that pass by the them who exceed the stipulated speed limit. So speed limits are good idea. To enforce these speed limit, laws have been passed making speed an offence and signs have been erected so as to indicate the maximum permissible speed. The police can't be every where to enforce the speed limit and so enforcement cameras are there to do this work. Nearly everyone slows down infront of the speed Camera. We finally have a solution to the speeding problem. Now if we are to assume that speed cameras are the only way to make driver's slowdown, and they work efficiently, then we would expect there to be a great number of these every were and that day would be highly visible and identifiable to make drivers slow down. Speed cameras are invariably hidden behind trees, road signs and often the first indication that one is passing through a speed camera point are the ruler marks painted on the carriageway or flash of the camera when it goes off. Speed cameras were introduced in west London in 1992 and following their success in reducing speed related crashes and injuries their use expanded to many other areas of Great Britain. The equipment is expensive to buy, operate and maintain and their support in prosecution procedures also draws substantial administration costs. However the costs are small compared to the benefits of the society and the economy. Speed cameras are recommended under use to reduce road casualties. Since these cameras save lives of road users, the speed camera is also known as" safety camera". Speed camera uses the basic principle of Doppler Effect and RADAR technologies. We can discuss the Doppler Effect in these speed cameras and other working in these cameras. INTRODUCING THE DOPPLER EFFECT

The device,i.e the first generation RADAR is not capable of determining the speed of the detected object. This was limited to measuring the movement of echo on the screen, which gave a rather inaccurate result. As an example consider a car that makes a sound with a fixed frequency. When you are in the car, you won't notice any variation in the frequency of the engine sound. However you stand at the side of the road and listen to the car when it drives past under identical condition you will notice that the frequency of the engines sound increases as the car comes nearer and then decreases as the car travels past you. It is a matter of common experience that the pitch of the note appears to change when either source or observers or both are in motion relative to each other. Either the source or the observer or both move relative to and each other, the apparent pitch produced by the sounding body appears to be higher than actual pitch. In the same way, when the source moving towards the observer or the observer moving away from this source or both moving away from each other the apparent pitch will appear to be lower than the actual pitch of the sounding body. The apparent change in frequency/pitch due to relative motion between source and observer is known as the Doppler's principle. For example: if a railway engine...
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