Which HCM edition do these thresholds follow?

The thresholds follow the Highway Capacity Manual 7th Edition (HCM 7e) Table 19-3 for signalized intersections: A ≤ 10, B ≤ 20, C ≤ 35, D ≤ 55, E ≤ 80, F > 80 seconds per vehicle.

Does this tool work for unsignalized intersections?

No. Unsignalized intersections (two-way stop, all-way stop, roundabouts) use different LOS thresholds per HCM Chapter 20 and 22. This tool is for signalized intersections only.

What is "average control delay"?

Average control delay is the additional travel time experienced by a vehicle due to the presence of a traffic signal, including deceleration delay, queue move-up time, stopped delay, and acceleration delay. It is expressed in seconds per vehicle (s/veh).

Can I enter decimal values?

Yes. You can enter values like 34.7 s/veh. The tool accepts any non-negative number.

What does LOS F mean in practice?

LOS F indicates a breakdown condition where demand exceeds capacity. Vehicles experience long queues, unpredictable delays often exceeding 80 s/veh, and the intersection is considered to be operating under forced flow.

Is this tool accurate enough for a formal traffic study?

This tool correctly applies the HCM thresholds and is suitable for verifying or illustrating LOS grades. For a formal traffic impact study, always use certified software (Synchro, HCS, etc.) and a licensed traffic engineer.

Level of Service (LOS) Helper

Enter average control delay (seconds/vehicle) to instantly get the HCM Level of Service grade (A–F) for a signalized intersection.

Signalized Intersection LOS

Enter the average control delay from your traffic study or simulation output.

Average Control Delay (s/veh)

Enter a delay value and click Get LOS

Thresholds per HCM 7th Edition, Table 19-3 — Signalized Intersections only.

HCM LOS Reference Table

Signalized intersection LOS grades per HCM 7th Edition.

LOS	Control Delay (s/veh)	Description

LOS F applies when demand exceeds capacity regardless of delay value.

Summary

The Level of Service (LOS) Helper determines the HCM Level of Service grade for signalized intersections using average control delay per vehicle (seconds/vehicle). LOS grades range from A (excellent flow, delay ≤ 10 s/veh) to F (forced flow, delay > 80 s/veh). The thresholds follow the Highway Capacity Manual (HCM 7th edition) Table 19-3 for signalized intersections.

How it works

Enter the average control delay per vehicle in seconds (from a traffic study or simulation output).
The tool compares your delay value against HCM 7th edition LOS threshold table.
The LOS grade (A through F) is displayed immediately with a color-coded badge.
A reference table shows all six LOS grades and their delay ranges for context.
Use the result to evaluate intersection performance or support a transportation study.

Use cases

Quickly classify intersection performance from a traffic count or simulation.
Verify LOS grades during transportation impact study preparation.
Teach students the HCM LOS concept with an interactive reference.
Cross-check outputs from traffic software such as Synchro or VISSIM.
Screen multiple intersections by pasting delay values one at a time.
Document LOS results in traffic engineering reports.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu