What does "overlapping" mean in the context of vehicle speed detection?

In the context of vehicle speed detection, "overlapping" refers to the scenario where two vehicles are simultaneously detected by the speed measurement system. This situation complicates the accuracy of speed readings because the system can struggle to differentiate between the two vehicles. The presence of multiple signals or reflections from nearby vehicles can lead to confusion in the data collected, making it difficult to ascertain the correct speed of each individual vehicle. This overlap can result in erroneous speed readings that do not accurately reflect the true speeds of the detected vehicles.

In contrast, the other options describe different situations: detecting speed in crowded areas, a vehicle being detected twice, or vehicles moving at the same speed. Each of these scenarios does not specifically pertain to the complications arising from simultaneous detection, which is the core concept of overlapping in speed detection.