What is signal coordination index?

• A. A metric to measure how quickly vehicles pass a point at a signal.
• B. A measure of average delay per vehicle at a single signal.
• C. A metric to evaluate how well signals along a corridor are timed for progression.
• D. A gauge of pedestrian crossing times at intersections.

Answer: (C)

Signal coordination index measures how well signals along a corridor are timed to allow smooth progression from one intersection to the next. It captures how well cycle lengths and offsets are aligned so vehicles encounter consecutive greens with minimal stops, essentially evaluating the effectiveness of a “green wave” across multiple signals. A high index means good progression and steady flow along the corridor; a low index indicates poor coordination and frequent stops or speed adjustments. This concept is about coordinating a series of signals, not just how fast vehicles pass a single point, nor the average delay at one intersection, nor pedestrian crossing times. So it best reflects the overall timing plan for a corridor rather than individual intersection performance.