What are the two main types of speed detection devices used by law enforcement?

The main types of speed detection devices used by law enforcement are radar and lidar. Radar operates by emitting radio waves and measuring the time it takes for them to bounce back after hitting a moving vehicle. This allows officers to determine the speed of the vehicle based on the Doppler effect, where the frequency of the waves is altered depending on the speed of the object moving towards or away from the source.

Lidar, on the other hand, uses laser light pulses to measure the distance between the device and a vehicle. By calculating the time it takes for the light to return after reflecting off the vehicle, lidar can also ascertain the speed of the vehicle. Lidar is known for its precision and ability to target specific vehicles in traffic, making it a valuable tool for law enforcement.

The other options, while mentioning some elements related to speed detection, do not primarily represent the two main technologies in use for this purpose. Cameras may be involved in monitoring speed but are generally not the main detection tools in the same context as radar and lidar. GPS is also used for various tracking purposes but does not provide the instantaneous speed measurements like radar and lidar.