Level of service is a letter-based measure describing selected operating conditions for a transportation facility under a defined analysis method.
Definition
Level of service, often shortened to LOS, uses letter grades to describe selected operating conditions for a road, intersection, or other transportation facility. The measures behind the grade depend on the facility and analysis framework. They may address factors such as delay, but the label alone does not explain which measure, inputs, or assumptions produced it. A firm should identify the method, study period, and conditions represented when reporting LOS. Agencies may use the result alongside other measures to evaluate a project. LOS is not a complete measure of safety, accessibility, comfort, or policy goals, and it does not capture every traveler’s experience. Firms may analyze different peak periods or apply different agency criteria, so comparisons require consistent methods. For a broader view of travel needs, teams may pair LOS with multimodal analysis only when the project scope supports it.
How owners use it
- Explain the analysis method and assumptions behind an LOS grade in a report.
- Compare facility conditions across defined scenarios using the same measure and period.
- $180 seconds of delay per vehicle - 120 seconds = 60 seconds of additional delay in the second scenario.
- Clarify to a client that an LOS grade is one operating measure, not an overall judgment of a street.
