What is a "speed trap"?

A speed trap refers to a designated location where law enforcement uses radar technology to monitor and enforce speed limits. This practice typically involves positioning radar equipment in areas where vehicles are likely to exceed the speed limit, allowing officers to detect and pull over speeders effectively. Speed traps are often situated in locations that have a history of speeding violations or in areas where safety concerns are significant, such as school zones or high-traffic intersections.

The other options describe different concepts or types of radar that are not focused on the enforcement of speed limits. For instance, a type of radar used in slow-moving traffic may refer to specialized equipment designed for unique traffic conditions but does not capture the idea of monitoring violations at a specific site. Similarly, a device measuring pedestrian speed does not relate to vehicle speed enforcement. Lastly, a radar system created for long-range tracking is more focused on broader surveillance or tracking tasks, rather than the enforcement of speed limits at a specific location. Thus, the definition of a speed trap aligns perfectly with the function described in the correct option.