Define "queue length" in traffic operations.

Queue length refers specifically to the number of vehicles that are waiting in line to pass through an intersection or merge point. This measurement is critical in traffic operations as it helps engineers understand the extent of congestion at a given location, assess the effectiveness of traffic control devices, and evaluate the need for capacity improvements.

When analyzing traffic flow, knowing the queue length can inform decisions related to signal timing, roadway design, and traffic management strategies. For instance, a longer queue length may suggest that traffic demand exceeds the available capacity at a particular intersection, prompting adjustments to signal phases or the consideration of alternative traffic configurations. This metric provides insight into traffic behavior and can highlight areas that may require further study or intervention to improve overall traffic efficiency.