Environmental Benefits of Alternative Fuels and Advanced Technology in Transit

This report evaluates potential reductions in pollutant emissions and fuel consumption that could be achieved through greater adoption of alternative fuels including CNG, LNG and biodiesel, and advanced vehicle technologies such as hybrid electric drive systems in the national transit bus fleet. According with the analysis results, ongoing and planned procurements by transit agencies of new technology diesel, alternative fuel and hybrid-electric buses will result in reductions in emissions of CO, NMHC, NOx and PM with modest increases in CO2 emissions and fuel consumption over the next 3 years. Increased adoption above and beyond that occurring through the transit agencies own initiatives can further capitalize emissions and fuel economy benefits of new technologies. Hypothetical scenarios in which new “clean-diesel” (post-2007 model year), CNG, diesel-electric hybrid, gasoline electric hybrid and biodiesel fuel use were each individually increased to 15% of the U.S. fleet were considered. Potential changes in annual emissions and fuel consumption are presented. Benefits from the different technologies are discussed. Diesel-electric hybrid buses appear to offer the best overall environmental benefits and is the only technology to result in a reduction in fossil fuel consumption. The relative emissions and efficiency impacts benefits of the various technologies are presented for comparison.