Context: Traffic police have started using radio speed guns to crack down on speeding vehicles in Puducherry since September, 2023.
Relevance of the Topic: Prelims: Key facts about new emerging technologies being deployed (speed guns etc.); Basic understanding of Doppler Effect.
What is a speed gun?
- A speed gun is a device to measure the speed of a moving object without having to be in contact with the object.
- Working Mechanism: The device emits radio signals and calculates the Doppler shift in the reflected signals to precisely determine the speed of the vehicle.
What is the Doppler Effect?
- The Doppler effect (Doppler shift) is the change in frequency of waves as their source moves towards or away from a listener/observer. (It relies on the concept of relative velocity)
- E.g., A train approaching the platform sounds louder (higher frequency) than the train leaving (lower frequency) the station. This effect is the Doppler effect.
Working Mechanism of Radio Speed Gun:
- As the radio waves emitted by the gun hit a moving vehicle, the frequency of the reflected waves changes due to the relative motion between the gun and the vehicle. By analysing this frequency shift, the radar gun can determine the speed of the vehicle.
- The transmitter emits radio waves, which the person holding the speed gun can direct at an object.
- The receiver collects the waves reflected by the object back in the direction of the speed gun.
- If the object is approaching the speed gun, the frequency of the returning waves will be slightly higher than that of the transmitted waves.
- The simple computer in the gun can determine the object’s speed based on this difference. The faster the vehicle is moving, the greater the Doppler shift it will produce.
Utility:
Speed guns are widely used by:
- Law enforcement officials to monitor traffic speed
- Coaches to gauge the performance of their athletes
- Various other industries in need of accurate motion tracking.
Limitations of Radio Speed Gun:
- To ensure accurate speed measurements, radar guns require regular calibration. Factors such as the angle of the radar beam, weather conditions can impact the accuracy of the readings.
- It faces difficulty in detecting speeds in heavy traffic (may pick up signals from multiple objects).
LIDAR Speed Guns:
- The LIDAR (light detection and ranging) Speed Violation Detection System utilises laser pulses to accurately measure vehicle speed.
- By emitting lasers towards vehicles, the system calculates the bounce-back time to determine speed. This precise solution deters speeding and promotes compliance with speed limits.
- The system is more accurate than Radio speed guns as the laser light has very low divergence and thus offers better targeting.
With their advanced technology, the Radio speed guns as well as LIDAR speed guns are a vital tool for law enforcement agencies in ensuring safer roads.