Passenger travel was 4.7 percent more energy efficient in 2002 than in 1992 (figure 14-7). During the same period, however, freight energy efficiency declined by 2.2 percent.1
Improvements in domestic commercial aviation are the primary reason for the gains in passenger travel efficiency. For instance, improved aircraft fuel economy and increased passenger loads resulted in a 36 percent increase in commercial air passenger energy efficiency between 1992 and 2002. Domestic commercial air passenger-miles of travel (pmt) also rose 36 percent during this same period while energy consumption decreased by less than 1 percent .
Highway passenger travel—by passenger cars, motorcycles, and light trucks2—represented 87 percent of all pmt and 92 percent of passenger travel energy use in 2002. Overall, highway travel was 2.5 percent more efficient in 2002 compared with 1992. This gain was due to a 2.9 percent increase in the efficiency of passenger cars and motorcycles and a 3.3 percent increase in the efficiency of light trucks. For the period 1992 to 2002, passenger car and motorcycle pmt increased 19 percent while energy use increased 15 percent; concurrently light-truck pmt increased 39 percent while energy use rose 35 percent. The increase in energy efficiency in both cases can be explained by the faster growth in pmt coupled with a slower growth in energy use. For example, on an annual basis light-truck pmt grew faster than energy consumption during this period (3.5 vs. 3.1 percent) .
The decline in freight energy efficiency between 1992 and 2002 resulted from a 2.0 percent annual growth rate of ton-miles paired with a 2.3 percent annual growth rate in freight energy consumption (figure 14-8). Contributing to the overall trend was a decline in the energy efficiency of pipelines (-8 percent), waterborne transportation (-9 percent), and air transportation (-7 percent). However, during the same period, rail freight energy efficiency increased by 18 percent .
1. U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, calculations using data from table 14-7 and table 14-8 in appendix B of this report.
1 Passenger energy efficiency is measured in passenger-miles of travel per British thermal unit (Btu). Freight energy efficiency is ton-miles per Btu.
2 Light trucks include minivans, pickup trucks, and sport utility vehicles.