Emissions Benefits from Alternative Fuels and Advanced Technology in the U.S. Transit Bus Fleet

Abstract

Alternative fuels and technologies offer potential for reducing emissions in public transportation. These potentials were explored by determining emissions levels and fuel consumption from the U.S. transit bus fleet and comparison of hypothetical scenarios in which implementation of specific alternative fuels and technologies is considered. Impacts from current transit bus procurements were also evaluated. Emissions benefits above and beyond the natural course of transit bus procurements were examined for new diesel buses running on ULSD fuel, diesel-electric hybrid buses, gasoline-electric hybrid buses, compressed natural gas and biodiesel. According to the analysis, reductions in emissions of CO, NMHC, NO x , PM and CO 2 , as well as fuel consumption, may be attained, and diesel hybrid buses yield the largest reductions in CO 2 emissions and are the only technology to reduce fuel consumption relative to the present fleet. Introducing diesel-electric hybrid buses in 15% of the U.S. transit bus fleet would reduce annual end-use emissions by nearly 1,800 tons of CO, 400 tons of NMHC, 4,400 tons of NO x , 200 tons of PM, 491,400 tons of CO 2 , and fuel consumption by 50.66 millions of diesel gallons.