What is meant by 'lost time' in traffic signal operations?

• A. The total phase duration at an intersection
• B. Time lost due to vehicle starts and stops
• C. Time required for pedestrian crossings
• D. Time taken for emergency vehicle passage

Answer: (B)

Lost time in traffic signal operations refers specifically to the time lost due to vehicle starts and stops at intersections. This concept captures the inefficiencies that occur when vehicles must come to a complete stop at a red light and then accelerate again when the light turns green. This stop-and-go behavior impacts overall traffic flow and can contribute to congestion.

On the other hand, total phase duration encompasses the entire time allocated to a specific traffic signal phase, including green, yellow, and red phases, and does not target the specific inefficiencies that lost time aims to address. The time required for pedestrian crossings pertains mainly to the time allocated for pedestrians to safely cross the road, which is separate from the dynamics of vehicle movement. Additionally, the time taken for emergency vehicle passage accounts for the priority that emergency vehicles may receive at intersections, allowing them to clear the area as rapidly as possible, but this does not directly relate to the concept of lost time that occurs for typical traffic flow. Thus, the focus on vehicle dynamics and operational delays makes the understanding of lost time pivotal in traffic signal operations.