U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Fact #319: May 10, 2004
Highway Vehicle Emissions: 1970–2001 Comparison
Although the number of highway vehicles in the United States has more than doubled from 1970 to 2001, the emissions from those vehicles actually declined during that period of time. The graph shows the percent change from 1970 to 2001 for all highway vehicle emissions of carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and particulate matter smaller than 10 microns (PM10). It also shows the percent change in the number of highway vehicles. Vehicular emission controls along with changes in fuel properties have made it possible for twice the vehicles to emit less in 2001 than the vehicles did in 1970.
Total Highway Vehicle Emissions Change from 1970 to 2001 
Supporting Information
Highway Vehicle Emissions, 1970 and 2001
| |
1970
(Thousand Short Tons) |
2001
(Thousand Short Tons) |
Percent
Change |
| Carbon monoxide |
163,231 |
74,825 |
-54.2% |
| Nitrogen oxides |
12,624 |
8,249 |
-34.7% |
| Volatile organic Compounds |
16,910 |
4,874 |
-71.2% |
| Particulate matter |
480 |
218 |
-54.6% |
| |
|
|
|
| Number of highway vehicles |
111,242,295 |
235,331,382 |
111.5% |
|
Source: U.S. Environmental Protection Agency, National Emission Inventory (NEI) Air Pollutant Emission Trends.
Federal Highway Administration, Highway Statistics, Table VM-1.
Federal Highway Administration, Highway Statistics Summary to 1995, Table VM201a. |
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