Mass Transit

To help reduce air pollution in U.S. cities, various alternative fuels have been proposed for use in transit buses, including compressed natural gas, liquified natural gas, methane, ethanol, biodiesel fuel, and propane. GAO found that alternative fuel buses account for a very small, but growing, portion of the nation's transit bus fleet. Five percent of the nation's 50,000 transit buses ran on some type of alternative fuel in 1997. The most commonly used alternative to diesel fuel is compressed natural gas. Transit operators are also beginning to test new propulsion system technologies -- hybrid electric systems and fuel cells -- in their transit buses. Data are limited on the extent to which alternative fuels in transit buses have improved air quality in urban areas. Transit operators pay more to buy, maintain, and operate buses that use compressed natural gas than they pay for diesel buses. When deciding whether to switch to alternative fuels, transit operators consider a range of factors, including the need to adhere to more stringent emissions standards, public concerns about transit bus pollution, and the higher costs and reduced reliability of buses that use alternative fuels.

GAO noted that: (1) alternative fuel buses account for a very small, but growing, portion of the nation's transit bus fleet; (2) in 1997, 5 percent of the nation's approximately 50,000 transit buses operated on some alternative fuel system; (3) the most commonly used alternative to diesel fuel is CNG--accounting for an estimated 75 percent of the full-sized alternative fuel transit buses in 1998; (4) transit operators are also beginning to test and demonstrate new propulsion system technologies in their transit buses; (5) hybrid electric transit buses are available, and fuel cell buses will be commercially available by 2002; (6) data are limited on the extent to which alternative fuel transit buses provide air quality benefits in urban areas; (7) on a national scale, transit buses do not significantly affect air pollution levels because, according to the Department of Transportation, they constitute only about 0.02 percent of the approximately 208 million automobiles, trucks, and other vehicles in the United States; (8) however, because individual alternative fuel transit buses emit less pollution than do individual diesel buses, alternative fuel buses have some beneficial effect on the air quality of the urban areas in which they operate; (9) transit operators pay more to buy, maintain, and operate CNG buses than they pay for diesel buses; (10) operators that buy CNG buses typically pay approximately 15 to 25 percent more for each of these buses than they do for diesel buses; (11) the costs of installing fueling facilities and upgrading maintenance garages for CNG buses vary among transit operators; (12) however, constructing a compressed natural gas fueling station typically costs about $1.7 million, and modifying a maintenance facility typically costs about $600,000; (13) six of the eight transit providers GAO spoke with were able to provide operating cost estimates reporting higher operating costs, higher maintenance costs and higher fuel costs for their CNG buses than for their diesel buses; (14) transit operators approach the decision, of whether switch to alternative fuels by considering a range of factors, such as adhering to more stringent emission standards and the public's concerns about transit bus pollution; (15) factors such as the increased costs and reduced reliability of alternative fuel buses experienced to date discourage the use of fuels other than diesel; and (16) diesel buses have become significantly cleaner over the past 11 years, thereby reducing the environmental advantages of shifting to alternative fuel buses.