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The Northeast Area of the Postal Service recently completed an assessment of the environmental and economic impacts of deploying alternative fuel vehicles (AFVs) in Connecticut and Massachusetts. The study was conducted in accordance with procedures established by the President's Council of Environmental Quality (CEQ) to implement the National Environmental Policy Act (NEPA). This assessment produced a new computer model which is capable of comparing the environmental and economic impacts of various alternative fuel fleet options. The model was developed to be flexible in that it is able to compare various technologies and vehicle mixes and can also function as a data sensitivity testing program. The AFV assessment computer model provides the Postal Service with the tool needed to continually assess the environmental and economic impacts associated with rapidly changing AFV technologies.

The chemistry of unburned hydrocarbon oxidation in SI engine exhaust was modeled as a function of temperature and concentration of unburned gas for lean and rich mixtures. Detailed chemical kinetic mechanisms were used to model isothermal reactions of unburned fuel/air mixture in an environment of burned gases at atmospheric pressure. Simulations were performed using five pure fuels (methane, ethane, propane, n-butane and toluene) for which chemical kinetic mechanisms and steady state hydrocarbon (HC) emissions data were available. A correlation is seen between reaction rates and HC emissions for different fuels. Calculated relative amounts of intermediate oxidation products are shown to be consistent with experimental measurements.