Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
2-18
followed by motorcycles, passenger rail (which includes transit, commuter, and
intercity rail), commercial aviation, passenger cars, and light duty trucks.
Buses have the lowest emissions per PMT because of their high occupancy rate–
an average of about 21 people per bus, when including all types of bus service. 44
Transit buses have a lower occupancy rate—about 9 to 10 people per bus
averaged across the U.S. 45 However, transit buses only account for 15 percent of
all bus passenger-miles traveled. 46 Intercity passenger rail averages about 20
passengers per car, while rail transit averages 23, and commuter rail averages
31. 47 Light-duty vehicles average 1.6 persons per vehicle. 48
Commercial airliners
are very energy intensive per vehicle-mile traveled, but have slightly lower GHG
emissions per passenger-mile traveled than light-duty vehicle, due to the high
number of passengers per plane. Aircraft and inter-city rail may involve
additional auto or transit travel from the airport/station to the final destination;
the emissions from this leg of the trip are not included here.
44 U.S. Department of Transportation, Bureau of Transportation Statistics. National
Transportation Statistics, http://www.bts.gov/publications/
national_transportation_statistics/. Tables 1-32 and 1-37.
45 U.S. Department of Transportation, Federal Transit Administration. 2007 National
Transit Database.
46 Davis, S.C., S.W. Diegel, and R.G. Boundy (2008). Transportation Energy Data Book. Oak
Ridge National Laboratory, Oak Ridge TN (Table 2.12); U.S. Department of
Transportation, Bureau of Transportation Statistics. National Transportation Statistics,
http://www.bts.gov/publications/national_transportation_statistics/. Table 1-37.
47 Davis, S.C., S.W. Diegel, and R.G. Boundy, 2008 (cited).
48 U.S. Department of Transportation, Bureau of Transportation Statistics. 2001 National
Household Transportation Survey.