1993 = 100
|All other trucks||100||107||111||117||123||128||134||141||144||144||150|
|Ships and boats||100||99||102||99||71||60||78||116||79||106||106|
|Total, all modes||100||103||105||107||108||110||114||117||116||118||119|
|International bunker fuels||100||102||106||108||115||112||111||111||107||97||91|
make it easier to compare data of differing magnitudes over time, the Bureau
of Transportation Statistics divided the data for all years in each category
(see table 15-3b) by the initial year value and multiplied the result by
Highway total includes passenger cars, buses, light-duty trucks, and other trucks. Other carbon dioxide emissions are from motorcycles, construction equipment, agricultural machinery, pipelines, and lubricants. International bunker fuel emissions (not included in the total) result from the combustion of fuels purchased in the United States but used for international aviation and maritime transportation. Thus, aircraft and ships and boats data included in U.S. total emissions involve only domestic activities of these modes as do all other data shown. The large annual variations in ships and boats data may result from methodological problems related to the domestic/international partition of maritime emissions. Economic factors may also contribute.
Aircraft emissions consist of emissions from all jet fuel (less bunker fuels) and aviation gas consumption. Alternative-fuel vehicle emissions are allocated to the specific vehicle types in which they were classified (i.e., passenger cars, light-duty trucks, and other trucks and buses).