The lidar gun clocks the time it takes a burst of infrared light to reach a car, bounce off and return back to the starting point. By multiplying this time by the speed of light, the lidar system determines how far away the object is. Unlike traditional police radar, lidar does not measure change in wave frequency. Instead, it sends out many infrared laser bursts in a short period of time to collect multiple distances. By comparing these different distance samples, the system can calculate how fast the car is moving. These guns may take several hundred samples in less than half a second, so they are extremely accurate.The laser beam is very narrow, and not scattered like a microwave beam, and therefore it can be easily used in heavy traffic. Weather conditions affect it, and most laser guns cannot be used in a very heavy rainfall for example. The speed measurement relies heavily on the infrared laser beam reflected back from the vehicle. The most reflective vertical part on the front is the license plate, and this is mostly targeted.