What must be calibrated regularly to ensure accuracy in speed detection devices?

Calibration of radar and lidar devices is essential to maintain their accuracy in measuring the speed of moving vehicles. Over time, external factors such as environmental conditions, wear and tear, and changes in electronic components can affect the performance of these devices. Regular calibration ensures that the devices are functioning correctly and providing reliable speed readings.

When radar and lidar devices are calibrated, they are tested against known speed standards to ensure that they can accurately detect and measure the speed of vehicles within a certain margin of error. This process is crucial for maintaining the integrity of speed enforcement and ensuring that any enforcement actions based on the speed readings are justifiable and valid in legal contexts.

Other options may relate to speed detection in some way, but they do not play a direct role in the accuracy and effectiveness of the speed detection devices themselves. For instance, while the vehicle's engine might influence overall vehicle performance, it does not affect how radar and lidar devices measure speed. Similarly, speed limit signs, while important for informing drivers, do not require calibration and will not impact the accuracy of speed detection technologies. Lastly, while software used by police departments is important for analyzing data and managing records, it does not require the same type of regular calibration as the detection devices.