What is a turning movement count (TMC) and why collect it?

What is a turning movement count (TMC) and why collect it?

• A. A tally of overall traffic volume along a corridor.
• B. A count of pedestrian movements at intersections.
• C. A tally of volumes by movement at an intersection to support planning and timing.
• D. A survey of vehicle emissions at an intersection.

Answer: (C)

Turning movement counts track how many vehicles make each possible movement at an intersection—left, through, and right—from each approach. This kind of data shows how demand is distributed among the different movements, which is exactly what you need to set and adjust signal timing effectively. By knowing the volume for each movement, engineers can size green times, decide whether to use protected left turns, and optimize cycle length and progression to minimize delays and improve throughput. Counts are typically collected during peak periods and can come from manual observations or automated methods, but the key point is that they break down volumes by movement at a specific intersection, not just the total traffic along a corridor, pedestrian counts, or emissions.

Turning movement counts track how many vehicles make each possible movement at an intersection—left, through, and right—from each approach. This kind of data shows how demand is distributed among the different movements, which is exactly what you need to set and adjust signal timing effectively. By knowing the volume for each movement, engineers can size green times, decide whether to use protected left turns, and optimize cycle length and progression to minimize delays and improve throughput. Counts are typically collected during peak periods and can come from manual observations or automated methods, but the key point is that they break down volumes by movement at a specific intersection, not just the total traffic along a corridor, pedestrian counts, or emissions.