Photo Radar Technology Essay

Speeding vehicles passing through school zones and neighborhoods compromises the safety and livability of an individual. Most of the time it poses threat to children playing outdoor, it makes bicycling, walking, and even driving dangerous to all. Through the years speed enforcement was implemented to regulate speeding vehicles. One of the oldest methods was the time distance method wherein three police officers were posted in three dummy tree trunks at a one mile interval and used stop watch to monitor the speed of a vehicle. But through the advent of technology the use of cameras such as speed, red-light, bus lane, toll- booth, level crossing, and congestion charge cameras; a vehicle detection system such as piezo-electric strips, laser, optical character recognition, and Doppler radar, and integrated with the process of implementing state rules and regulations in regulating speed limit provides a more effective means of implementing speed enforcement. The photo radar is an automated photographic speed enforcement technology that has the capability of identifying vehicles above a speed limit using a camera and detector equipment. The unit is a combination of a high speed camera with a flash unit and a low powered narrow beam Doppler antenna which is aimed across the road together with electronic controls and computers to detect, photograph, and record the time, date, speed, and location of the vehicles exceeding a determined speed limit. It can photograph the face of the driver and the license plate at the front side if the unit is intended or deployed at the oncoming traffic and the license plate at the rear side if deployed at the receding flow. The license number will be extracted from the photograph and the registered owner will receive a citation usually by mail within six working days and the violator has to respond within 30 days upon receiving. The recipient has three courses of actions to consider, either pay the fine, attend a court hearing, or file a certificate of innocence. The system starts to work due to the triggering of the radar sensor which causes the high speed cameras to take photographs. In a simple explanation, radar is considered a device that utilizes electromagnetic waves to be able to identify the direction, location, and speed of both in motion or a fixed object. Radio waves are being emitted at the transmitter part and will be reflected by the target. It will then be received by a receiver commonly being located together with the transmitter. The received or the returned radio signal is amplified due to its weak signal thus enabling the radar to detect specific objects at ranges where sound or visible light are too weak to be detected. If a solid object exists in air or vacuum, electromagnetic waves reflect or scatter between the surrounding and the object since this wave reflects in a very large change in the dielectric or diamagnetic constant and also in a change in the atomic density. This phenomenon applies to metal and carbon fiber wherein its electrical conductivity makes radar well suited for the detection of ships, aircrafts, and vehicles. The Doppler radar is one type of radar that operates in-line with the principle of Doppler Effect wherein it is the change in the wavelength or in the frequency of a wave being perceived or observed relative to the motion of the source of the wave. The equipment measures accurately the target’s radial velocity through the shifting of the received frequency up and down by means of the directional beam of the antenna. For instance the moving target is a car and as it recedes from the source, the speed of the car can be measured by firing a beam towards it. The beam is in the form of a radio frequency signal and each wave has to travel in succession to be able to reach the car before it can be reflected and re-detected by the source. As the wavelength increases, the gap between each wave also increases due to the waves moving further. Consequently if the car is approaching, the wavelength will be lesser and also the gap. In either way, computations from the Doppler Effect will determine accurately the velocity of the car. Put it analogously if a person catches a baseball every second with constant velocity, the balls will be received frequently if the thrower is moving towards and less frequent if the thrower is moving away from the catcher. Therefore the affected part is the wavelength and the perceived frequency. Doppler Effect is only capable of determining the speed of the target relative along the line of sight of the target and the radar; furthermore any velocity perpendicular to this line sight will not be determined. Doppler radars may be classified as of a continuous wave type, coherent pulse type, and frequency modulated. Continuous wave radar operates by sending out a known frequency of very pure signal. Though it cannot determine the range of the target, it is ideal in determining the target velocity’s radial component. It is commonly used in traffic enforcement wherein the range is not considered and a quick and accurate measurement of the speed of the vehicle is important. Coherent pulsed or phase synchronized is another way of measuring the speed of an object. Due to Doppler Effect, the returned signal emanating from the target are being shifted away from the base frequency thus enabling the speed of the target relative to the radar be calculated. The Frequency modulated- Continuous wave Doppler radar is capable of sweeping the frequency of the transmitter to determine and encode the range. The range rate is a velocity accurately measured by the combination of the Doppler processing to pulse radars. A target cannot be detected if the range rate reflects a frequency almost near to the frequency of the transmitter and if the target is moving tangentially to the radar beam. Pulse Doppler radar is a combination of a high velocity and long range measurement capabilities. It uses a medium to high pulse repetition frequency usually in a 30 KHz interval. This allows the precise measurement of velocity in high resolution and detection of speeding targets. Speed Cameras consists of a flash unit and is capable of taking photographs of speeding vehicles once triggered by the radar sensor. The time, date, speed, and location are also recorded together with the photo. Compared to other methods of traffic enforcement, it does not require motorists to pull over once the violation is committed. Most of the time speed cameras are installed or deployed either mobile or fixed. If deployed mobile, it is usually attached to the police officers vehicle and roams around various places. Fixed cameras are installed along specific roadway places. Photo radar differs slightly from conventional radar due to the beam width. The width of the beam of a photo radar across a roadway is narrower compared to the width of the conventional radar. This enables the detection to be more specific one vehicle at a time. In the case if there are more vehicles in the beam, the camera will not be triggered to take photographs as seen on the diagram below.