Regional On-Road Mobile Source Emissions Characterization for Conventional and Alternative Vehicle Technologies

Abstract

The development of alternative fuels and vehicle technologies could lead to reductions in emissions and reduced reliance on petroleum fuels. The objectives of this study are to evaluate the potential reductions in air pollutant emissions associated with real world operation of future vehicles that utilize advanced fuels or technologies in comparison to conventional vehicles. For light duty vehicles, the fuels or energy sources considered are gasoline, ethanol (E85), compressed natural gas, hydrogen, and electricity. The technologies considered are internal combustion engines, hybrids, fuel cell, and electric vehicles. For heavy duty vehicles, biodiesel is considered for trucks and compressed natural gas is considered for buses, in addition to conventional diesel fuels and technologies. For most of the vehicle fuel and technology combinations, modal fuel use and emissions models were developed based on available second-by-second portable emission measurement system (PEMS) or dynamometer tailpipe emissions data.

Link-based average emission rates were estimated for different link-based average speeds and roadway types based upon second-by-second speed profiles measured on the road as part as previous PEMS measurements, supplemented by data from the literature in some cases. The results enable comparison of different vehicle technologies and fuels for each of several link-based average speeds and roadway facility types.

The linked-based emissions factors are coupled with the outputs of a transportation demand model for emission inventory estimation and assessment of the potential changes in emissions that can accrue from technology and fuel use. The results will provide support for decision making regarding alternative fuels, adoption of new vehicle technologies, and air quality management.