| Source
Classification | Tons of Nitrogen Oxides emissions |
|---|
|
| Highway Vehicles - Gasoline
|
4,955,567 |
| Highway Vehicles - Diesel
|
3,634,520 |
| Off-highway Vehicle Diesel
|
2,671,807 |
| Railroad Equipment
|
1,208,615 |
| Marine Vessels, Commercial
|
1,006,193 |
| LPG
|
206,365 |
| Aircraft
|
174,829 |
| Off-highway Vehicle Gasoline, 4-Stroke
|
141,344 |
| Pleasure Craft
|
68,332 |
| CNG
|
28,903 |
| Off-highway Vehicle Gasoline, 2-Stroke
|
8,569 |
| Marine Vessels, Military
|
438 |
|
