TRANSPORTATION ENERGY DATA BOOK: EDITION 20 - Center for ...

I
The transportation sector accounted for over half of the nation ‘s nitrogen oxide (NOx) emissions in
1998, with the majority coming jiom highway vehicles. For details on the highway emissions qf NOx,
see Table 4.5.
Table 4.4
Total National Emissions of Nitrogen Oxides, 1970-98”
(million short tons)
Percent
of total,
Source category 1970 1980 1990 1995 1997 1998 1998
Highway vehicles 7.39 8.62 7.09
Railroads 0.50 0.73 0.93
Other off-highway
1.44 2.80 3.88
Transportation total
Stationary fuel combustion total
9.32 12.15
10.06 11.32
7.83 7.88
0.99 0.95
4.14 4.30
11.89 12.95 13.13 13.05
10.89 10.83 10.40 10.19
Industrial processes total
0.78 0.56 0.80 0.77 0.79 0.80
Waste disposal and recycling total 0.44 0.11 0.09 0.10 0.10 0.10
Miscellaneous total 0.33 0.25 0.37 0.27 0.41 0.33
Total of all sources 20.93 24.38 24.05 24.92 24.82 24.45
Source:
U. S. Environmental Protection Agency, National Air Pollutant Emission Trends, 1900-1998,2000,
pp. A-6-A-10, and annual. (Additional resources: www.epa/oar/oaqps)
Note:
Emission estimation methodology changes indicated by shaded areas. Transportation methodologies
changed in 1970, while all others changed in 1990.
“The sums of subcategories may not equal total due to rounding.
TRANSPORTATIONENERGYDATABOOK: EDITION~O-2000
7.77
0.95
4.33
31.8%
3.9%
17.7%
53.3%
41.7%
3.3%
0.4%
1.3%
100.0%
4-5