American Institute of Certified Planners (AICP) Practice Exam

What Level of Service (LOS) is indicated by roadway delays per vehicle between 40 and 60 seconds?

1. LOS A

2. LOS C

3. LOS D

4. LOS F

The correct answer is: LOS D

Level of Service (LOS) is a qualitative measurement used to assess the operational conditions of a roadway and the quality of traffic flow. It ranges from LOS A to LOS F, where LOS A represents the best operating conditions and LOS F indicates complete breakdown or failure of flow. When delays per vehicle are measured between 40 and 60 seconds, this indicates a considerable level of congestion that affects the efficiency of traffic movement. Specifically, LOS C is characterized by acceptable delays, but with a noticeable decrease in the quality of service where drivers begin to sense congestion. When congestion exceeds this threshold and reaches delays of more than 40 seconds, it typically transitions to LOS D, which indicates increasingly severe congestion and longer delays. Therefore, identifying roadway delays between 40 and 60 seconds aligns with the definition and characteristics of LOS C, as it reflects a situation where traffic flow is stable, but conditions are approaching significant congestion that could lead to more serious delays. This understanding is essential for planners as it informs decisions regarding traffic management and roadway improvements.