Which aspect is checked by the CMU and MMU to ensure the intersection operates correctly?

The correct choice is related to timing functions, which are critical for ensuring that traffic signals operate correctly at intersections. Timing functions dictate how long each signal remains red, yellow, or green, directly affecting traffic flow and safety. The Central Management Unit (CMU) and the Master Management Unit (MMU) work together to monitor and adjust these timing functions based on real-time traffic data and patterns. By ensuring that the timing is accurate and optimized, the intersection can effectively manage the movement of vehicles and pedestrians, reducing congestion and minimizing the risk of accidents.

While traffic density, weather conditions, and signal maintenance are all important factors in traffic signal management, they do not pertain directly to the operational timing of signals at an intersection. Traffic density impacts how signals might be adjusted, weather conditions are external factors that can influence driving behavior, and signal maintenance ensures that the hardware is functioning correctly, but these aspects do not directly control how long the lights change at intersections, which is the specific focus of the timing functions.