Vehicle detectors are an important part of modern traffic control systems. Therefore while choosing vehicle detector different parameters like types of traffic flow data, their reliability, consistency, accuracy and precision and the detector response time should be considered.

Introduction

Over speeding of vehicles is one of the major contributing factors for road crashes and fatalities around the world. Even in India, it is one of the prime factor which increases both the probability of crash occurrence and the severity of its consequences, many a times leading to loss of life. To overcome the issue of over speeding, a need of Speed violation detection system is suggested. This is basically a part of Intelligent Traffic Enforcement Systems which has a centralised approach to modern traffic management.

There are various technologies available in the market for detection of speed now-a-days, mainly;

l  Radar based Speed Detection System

l  Laser based Speed Detection System

l  Video based Speed Detection System

Now the main question is which one to choose as per the Indian traffic road scenario? Below are two images showing the traffic scenario on roads.

Radar based speed detection system works on the principal of Doppler Effect. The device emits a radio wave at a set frequency which is then reflected by the target vehicle. The frequency of the reflected radio waves by the vehicle is different from the transmitted waves. From that difference, speed of the vehicle is calculated.

Laser based Speed detection System emits a narrow, focused Laser beam consisting of a series of pulses that are reflected back from the target vehicle.

The time for these pulses to return is measured thus, resulting in the calculation of speed of vehicle. Basically, it measures the round-trip time for light to reach a Vehicle and reflect back.

Disadvantages of Radar and Laser based Speed Detection Systems

  • Cosine Factor- Radar and laser based speed detection systems will record the true speed, only if they are in the line of the vehicles path which is NOT suitable for Indian roads i.e. non-lane based traffic scenario on roads.
  • If the radar is positioned at an angle to the path of the vehicle, the apparent speed of the vehicle is reduced. The reduction in speed is proportional to the cosine of the angle. Radar gun or Radar based speed system cannot differentiate between two vehicles that are at different speed, but are adjacent to each other. Hence, the speed detected through this system cannot be relied upon for evidence in the Indian court of law.
  • Laser works well when triggered straight to the Vehicle, while in Gantry architecture it is not following its own principle, hence its accuracy cannot be relied upon.
  • Both Laser and Radar system is calibrated while running parallel to the ground and in the direction of the moving vehicle, whereas when it is fitted at 6.5mtrs height it is in contradiction to its calibrating methodology.
  • Both Laser and Radar system requires yearly calibration. Since, these systems are not manufactured in India it will have to be sent abroad for calibration, which means system will not work during that course of time.
  • Both Laser and Radar system requires at least 3 feet of horizontal separation between two vehicles to detect speed, which is not really possible in bumper to bumper traffic as seen on Indian roads.

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