In Level of Service ratings for signalized intersections, which letter denotes the worst service?

• A. A
• B. F
• C. C
• D. B

Answer: (B)

Level of Service for signalized intersections is a rating of performance based on average delay per vehicle. The scale runs from A (best) to F (worst). As delay increases, the service level drops from A toward F. The worst service is the category that describes the highest delays, which signals unacceptable operation with long queues and poor progression. In practice, this worst category corresponds to very high delay per vehicle (roughly on the order of 80 seconds or more). So the correct choice is the one that describes that extreme, highest-delay category.