Which two types of speed detection devices are commonly used by law enforcement?

The correct response identifies radar and Lidar as the most commonly used speed detection devices in law enforcement. Radar operates by emitting radio waves that reflect off moving vehicles; the device calculates speed by measuring the frequency change between the emitted and reflected waves, known as the Doppler effect. This method is well-established and effective over varying distances.

Lidar, or Light Detection and Ranging, uses laser light instead of radio waves. It sends out pulses of laser light and measures how long it takes for the light to return after bouncing off a vehicle. This technology provides high accuracy and can target specific vehicles even in heavy traffic, making it a valuable tool for speed enforcement.

In contrast, options involving speed bumps and traffic lights do not serve as detection devices; they serve more as traffic calming measures or control mechanisms rather than active speed measuring tools. Similarly, while GPS and infrared sensors can provide valuable data in other areas, they are not primarily used by law enforcement for direct speed detection on the road. Thus, radar and Lidar remain the primary tools for officers conducting speed enforcement.