Add Lane Group
Advanced inputs (optional)
Notes: HV% reduces saturation flow using a simple heavy-vehicle factor; lane width applies a small saturation adjustment; arrival type scales delay.
Intersection Settings
Advanced (optional)
Defaults are applied when you add a new lane group. You can override per lane group below.
Lane Groups
| Label | v (veh/hr) | g (s) | seff (veh/hr) | c (veh/hr) | v/c | Delay (s/veh) | LOS |
|---|
Disclaimer: This tool provides educational, simplified, HCM-inspired estimates. It is not a replacement for official HCM software or professional engineering judgment.
How the math is done (high level)
- Capacity: c = seff · (geff/C), where seff starts from a base saturation flow and applies simple adjustments (HV%, lane width), then multiplies by lanes.
- v/c: X = vadj/c, where vadj = (v · multiplier)/PHF.
- Delay: uniform delay from a Webster-style form + a simplified overflow component; arrival type scales delay.
- Intersection delay: weighted average: dint = Σ(v · d)/Σv.
- LOS: based on signalized thresholds (A ≤ 10, B ≤ 20, C ≤ 35, D ≤ 55, E ≤ 80, F > 80 sec/veh).
What is Level of Service (LOS)?
Level of Service (LOS) is a qualitative measure used in traffic engineering to describe operational conditions at a signalized intersection. For signalized intersections, LOS is based on average control delay per vehicle and is graded from LOS A (very low delay) to LOS F (excessive delay).
This calculator allows you to first analyze a single lane group (such as an eastbound through movement), then combine multiple lane groups to compute an intersection-wide LOS using a weighted average delay approach.
How This LOS Calculator Is Typically Used
- Homework & exams: Analyze one lane group at a time to understand delay and v/c.
- Intersection analysis: Add all approaches and movements to compute overall LOS.
- What-if scenarios: Adjust green time, volumes, or heavy vehicles to see impacts.
Frequently Asked Questions
Is this an official HCM calculator?
No. This tool provides educational, HCM-inspired estimates and is not a substitute for
official HCM software or professional engineering judgment.
How is intersection LOS calculated?
Intersection LOS is computed using a weighted average of lane-group delays,
where each delay is weighted by its traffic volume.
What delay corresponds to each LOS?
A ≤ 10 s/veh, B ≤ 20, C ≤ 35, D ≤ 55, E ≤ 80, F > 80 s/veh.
What is Level of Service (LOS)?
Level of Service (LOS) is a qualitative measure used in traffic engineering to describe operational conditions at a signalized intersection. For signalized intersections, LOS is based on average control delay per vehicle and is graded from LOS A (very low delay) to LOS F (excessive delay).
This calculator allows you to first analyze a single lane group (such as an eastbound through movement), then combine multiple lane groups to compute an intersection-wide LOS using a weighted average delay approach.
How This LOS Calculator Is Typically Used
- Homework & exams: Analyze one lane group at a time to understand delay and v/c.
- Intersection analysis: Add all approaches and movements to compute overall LOS.
- What-if scenarios: Adjust green time, volumes, or heavy vehicles to see impacts.
Frequently Asked Questions
Is this an official HCM calculator?
No. This tool provides educational, HCM-inspired estimates and is not a substitute for
official HCM software or professional engineering judgment.
How is intersection LOS calculated?
Intersection LOS is computed using a weighted average of lane-group delays,
where each delay is weighted by its traffic volume.
What delay corresponds to each LOS?
A ≤ 10 s/veh, B ≤ 20, C ≤ 35, D ≤ 55, E ≤ 80, F > 80 s/veh.