How the speed guns work to calculate the speed of specific vehicle in the traffic?

Answer 1

The officer points it at you, when he pulls the trigger it sends either a Radar signal or Laser Light.

Radar hits your car, and bounces off. Echo and Doppler Shift occur, and are explained below, an excerp from the reference web sites (read the second one for laser):


When you shout into a well, the sound of your shout travels down the well and is reflected (echoes) off the surface of the water at the bottom of the well. If you measure the time it takes for the echo to return and if you know the speed of sound, you can calculate the depth of the well fairly accurately.

Echo is something you experience all the time. If you shout into a well or a canyon, the echo comes back a moment later. The echo occurs because some of the sound waves in your shout reflect off of a surface (either the water at the bottom of the well or the canyon wall on the far side) and travel back to your ears. The length of time between the moment you shout and the moment that you hear the echo is determined by the distance between you and the surface that creates the echo.

Doppler shift is also common. You probably experience it daily (often without realizing it). Doppler shift occurs when sound is generated by, or reflected off of, a moving object. Doppler shift in the extreme creates sonic booms (see below). Here's how to understand Doppler shift (you may also want to try this experiment in an empty parking lot). Let's say there is a car coming toward you at 60 miles per hour (mph) and its horn is blaring. You will hear the horn playing one "note" as the car approaches, but when the car passes you the sound of the horn will suddenly shift to a lower note. It's the same horn making the same sound the whole time. The change you hear is caused by Doppler shift.

Here's what happens. The speed of sound through the air in the parking lot is fixed. For simplicity of calculation, let's say it's 600 mph (the exact speed is determined by the air's pressure, temperature and humidity). Imagine that the car is standing still, it is exactly 1 mile away from you and it toots its horn for exactly one minute. The sound waves from the horn will propagate from the car toward you at a rate of 600 mph. What you will hear is a six-second delay (while the sound travels 1 mile at 600 mph) followed by exactly one minute's worth of sound

Answer 2

A radar gun is a small Doppler radar used to detect the speed of objects. A radar gun does not return position or power information. It relies on the Doppler effect applied to a radar beam to measure the speed of objects it is pointed at.

Radar guns may be hand-held or vehicle-mounted. Common uses include traffic speed law enforcement and measuring speeds in sports.

Most of today's radar guns operate at X, K, Ka, and (in Europe) Ku bands. An alternative technology, LIDAR, uses pulsed laser light.

There are radar detectors on the market which can detect most of police radar and laser systems. Conversely, in the spirit of electronic warfare, some police radars are equipped with detectors of operating radar detectors.

[edit]
How radar guns work
Radar guns are, in their most simple form, radio transmitters and receivers. They send out a radio signal, then receive the same signal back as it bounces off the objects. However, the radar beam is different when it comes back and from that difference the radar gun can calculate vehicle speed.

A radar beam is similar to the beam of a flashlight as it spreads out as the distance from the signal origin increases. The signal then bounces off objects in the path of the beam and are reflected back to the gun. The gun uses the doppler effect to calculate the speed of the object in the beam's path.

All bands of radar work the same, they simply operate on different frequencies. X band guns are becoming less common due to the fact the beam is strong and easily detectable. Also most automatic doors run radar using X band and can possibly affect the readings of police radar. As a result K band and Ka band are most commonly used by police agencies.

[edit]
Problems with radar guns
Although radar is an effective tool to acquire an object's speed, there are problems with it. Today's technology is relatively effective and error free so most inaccurate speed measurements are caused by the user.

For speed to be accurately calculated the object whose speed is desired should be the only moving object in the beam of the radar. If this is not the case it is impossible to determine which object's speed the system is reading. The angle in which the object is in relation to the radar source can also affect the reading. This includes angles on a horizontal and vertical plane.

Answer 3

Speed guns work by baouncing a lser off the car, the time that it takes for the laser to bounce from the gun to the car and back after each burst of light calaculates the speed of the car. Contrary to popular belief there is no way to trick the laser.

Answer 4

they send a wave to your car, and it measures the amount of time it takes for that beam to bounce back to the radar gun, so much distance and so long can give you the speed as for the traffic the just point the gun at YOUR car lol... not that hard to pick out 1 in 20 cars, just ur un-lucky day... its a true story

Answer 5

radar (microwave), using the doppler frequency shift to calculate the speed.

Answer 6

Doppler effect with radar (or light).
check this:
http://en.wikipedia.org/wiki/Radar_gun