Smog Calculator
Smog results from nitrogen oxides and volatile organic compounds reacting under sunlight. Model daily emissions and potential ozone formation from urban traffic scenarios.
Modern gasoline vehicles emit ~0.3–0.7 g/mile; heavy-duty vehicles higher.
Adjust to represent local atmospheric chemistry (1.0–1.5 typical).
Daily NOₓ emissions
1,890 kg/day
Daily VOC emissions
1,350 kg/day
Ozone formation potential
3,888 kg/day
Annual smog-forming emissions
1,419.12 metric tons
Trees needed to absorb equivalent NOₓ
101,365,714 trees
How to Use This Calculator
Gather traffic data
Estimate the number of vehicles, average trip distance, and trip frequency in the area of interest.
Set emission factors
Use emission inventory data or regulatory values for NOx and VOC emissions per mile.
Evaluate smog potential
Review daily and annual smog-forming emissions and compare them to mitigation targets or tree planting offsets.
Formula
Daily NOₓ = Vehicles × Trips × Distance × NOₓ Factor ÷ 1000
Daily VOC = Vehicles × Trips × Distance × VOC Factor ÷ 1000
Ozone Potential = (NOₓ + VOC) × Formation Factor
Example: 75,000 vehicles traveling 18 miles twice daily with 0.7 g/mile NOx and 0.5 g/mile VOC emit ~1,890 kg NOx and 1,350 kg VOC daily. With a 1.2 multiplier, ozone-forming emissions equal ~3,888 kg/day.
Adjust emission factors for fleet composition (diesel, EVs) to refine results.
About the Smog Calculator
Ground-level ozone and photochemical smog harm respiratory health. This calculator links transportation activity to smog-forming emissions for planners, policymakers, and advocacy groups.
When to Use This Calculator
- Urban planning: Estimate local smog impacts from roadway expansions.
- Air quality campaigns: Communicate benefits of transit, EV adoption, or car-free days.
- Environmental assessments: Evaluate smog mitigation for development proposals.
- Education: Demonstrate the link between vehicle activity and air quality.
Why Use Our Calculator?
- ✅ Scenario-ready: Test how reducing trips or changing fleet mix influences smog formation.
- ✅ Impact-focused: Converts emissions into tree-equivalent context.
- ✅ Customizable: Accepts local emission factors and atmospheric multipliers.
- ✅ Fast: Build quick estimates before detailed emission inventories.
Common Applications
Municipalities: Set air quality targets and measure progress toward cleaner transport.
Transit agencies: Highlight emission reductions from service expansions.
Corporate fleets: Calculate benefits of low-emission vehicles or telecommuting policies.
Tips for Best Results
- Combine with meteorological data for more precise ozone formation modeling.
- Use separate factors for peak vs. off-peak traffic if data is available.
- Include stationary sources to model total regional smog contributions.
- Calibrate with air quality monitoring data to validate assumptions.
Frequently Asked Questions
What is the ozone formation multiplier?
It approximates how NOx and VOCs combine to form ozone under sunlight. Values depend on local chemistry; adjust using regional smog models or literature.
How do electric vehicles affect results?
EVs have effectively zero tailpipe NOx/VOC. Decrease emission factors proportionally to the share of EV miles driven.
Do heavy-duty vehicles require different factors?
Yes. Set higher emission factors to represent diesel trucks or adjust vehicle count by class for accuracy.
Can I model construction emissions?
Yes. Replace vehicle counts and distance with equipment operating hours converted to equivalent mileage.