What is a “critical movement” at a signalized intersection?

• A. The movement with the smallest volume.
• B. The movement with the shortest green time.
• C. The movement that completes the fastest during cycle.
• D. The movement that determines the intersection’s capacity due to the highest delay.

Answer: (C)

In a signalized intersection, the key idea is which movement acts as the bottleneck that limits overall capacity. The critical movement is the one that experiences the greatest delay within a cycle, meaning it consumes the most of the cycle length relative to its service rate. This movement dictates how long the cycle must be and how many vehicles can be discharged from the intersection. It’s not about which movement has the smallest volume, which green time is the shortest, or which one happens to clear fastest. Those factors don’t inherently set the intersection’s capacity. The bottleneck, by definition, is the movement that causes the highest delay and thus determines the achievable throughput of the intersection.