Capacity results
Calculated street performance appears here.
Capacity utilization
Estimated lane configuration
Adjustment factors
| Factor | Value | Effect |
|---|
Baseline and proposed scenario
| Measure | Baseline | Proposed |
|---|
Recommendations
Calculation steps
Formula used
This is a planning-level model. Detailed design should use local standards, calibrated saturation flows, field observations, and qualified traffic engineering review.
How to use this calculator
- Select the street and control type.
- Enter lanes, dimensions, speed, and observed traffic.
- Add signal, traffic composition, and roadside conditions.
- Set future growth and proposed improvements.
- Calculate and review capacity, service level, and warnings.
- Export the results for planning discussions.
Example data
| Street condition | Lanes | Peak volume | Green ratio | Typical use |
|---|---|---|---|---|
| Residential collector | 2 | 650 veh/h | Not applicable | Neighborhood access review |
| Signalized minor arterial | 4 | 2,800 veh/h | 0.47 | Peak-hour capacity check |
| Downtown one-way street | 3 | 1,900 veh/h | 0.55 | Parking and pedestrian analysis |
| Transit-priority boulevard | 6 | 4,100 veh/h | 0.60 | Multimodal scenario planning |
Interpretation guide
| LOS | Approximate v/c range | Planning interpretation |
|---|---|---|
| A | 0.00–0.60 | Free flow with substantial reserve. |
| B | 0.61–0.70 | Stable flow with minor constraints. |
| C | 0.71–0.80 | Moderate demand and noticeable interaction. |
| D | 0.81–0.90 | Approaching unstable operation. |
| E | 0.91–1.00 | Operating near estimated capacity. |
| F | Above 1.00 | Oversaturated or breakdown conditions. |
Frequently asked questions
What does street capacity mean?
Street capacity is the estimated maximum sustainable traffic flow. It depends on lanes, controls, vehicles, and roadside activity.
Is this result suitable for final design?
No. The calculator supports early planning and screening. Final design needs local standards and professional review.
Why does signal timing reduce capacity?
Traffic moves only during effective green time. Lost time and competing phases reduce usable roadway time.
How are trucks and buses handled?
Heavy vehicles use passenger-car-equivalent adjustments. Their lower acceleration and larger size reduce effective capacity.
What is the peak-hour factor?
It represents traffic variation within the busiest hour. Lower values indicate sharper short-duration traffic peaks.
What is a volume-to-capacity ratio?
It compares adjusted demand with available capacity. Values above one suggest oversaturation or recurring queues.
How is daily capacity estimated?
Hourly capacity is divided by the selected K-factor. This provides a planning estimate, not a guaranteed limit.
Can the calculator compare road diets?
Yes. Enter a negative lane change and related improvements. Compare the proposed capacity and demand ratio.
Does pedestrian activity affect vehicle flow?
Yes. Frequent crossings can reduce turning capacity and green-time efficiency. The model applies a planning adjustment.
Why can parking removal improve capacity?
Parking maneuvers interrupt through traffic and use curb space. Peak restrictions may reduce those conflicts.
Assumptions and limitations
The calculator applies simplified adjustment factors for planning. It does not model queues, platoons, spillback, lane groups, or detailed gap acceptance.
Local capacity manuals may use different thresholds and equations. Confirm important decisions with observed data and qualified engineering analysis.
Road safety, accessibility, transit, walking, and cycling needs remain essential. Capacity alone should never determine a street design.