The correct answer is: C. flexible progressive system.
A flexible progressive system is a type of traffic signal system that adjusts the timing of the signals based on the current traffic conditions. This allows the system to keep traffic flowing smoothly, even during periods of heavy congestion.
A simultaneous system is a type of traffic signal system in which all of the signals in a given area are turned green at the same time. This can be helpful in reducing congestion at intersections, but it can also lead to problems with pedestrians and cyclists.
An alternate system is a type of traffic signal system in which the signals in a given area alternate between green and red. This can be helpful in reducing congestion at intersections, but it can also lead to problems with pedestrians and cyclists.
A simple progressive system is a type of traffic signal system in which the signals in a given area are timed to allow traffic to flow smoothly through the intersection. This can be helpful in reducing congestion at intersections, but it can also lead to problems with pedestrians and cyclists.
Flexible progressive systems are the most efficient type of traffic signal system because they are able to adjust to the current traffic conditions. This allows the system to keep traffic flowing smoothly, even during periods of heavy congestion.