Cleaning Up Diesel Pollution - Union of Concerned Scientists

38 lUnion of Concerned ScientistsAppendix ACALCULATING EMISSIONSNEW TRANSIT BUSEQUIVALENT EMISSIONSTo calculate new transit bus equivalentemissions, we assume a model year 2004diesel-powered urban transit bus will release10.34 grams per mile of nitrogen oxides and0.44 grams per mile of particulate matter. Theseemissions estimates are from Mark and Morey,2000. We also assume transit buses will average30,861 miles per year, based on the Departmentof Energy’s Transportation Energy Data Book(DOE, 2002).1999 EMISSION INVENTORYTo develop county-level emissions data formobile sources, we relied on the EPA’s finalemission inventory, available online at:ftp://ftp.epa.gov/EmisInventory/finalnei99ver2.However, we could not reconcile the EPA’s datafor off-highway emissions in California with datapublished by the California Air Resources Board(CARB). Since the EPA considers CARB’s datato be the most accurate, that is what we used.However, CARB provides information on reactiveorganic gases rather than volatile organiccompounds, and does not provide informationon PM 2.5emissions, which we assume makeup 99 percent of PM 10emissions.CASE STUDIESTo develop our emissions and cost estimatesfor the four types of equipment evaluated in ourcase studies, we relied on technical informationprovided by M.J. Bradley and Associates. Wealso used technical support documents associatedwith the EPA’s NONROAD model, located at:www.epa.gov/otaq/nonrdmdl.htm.To calculate the emission factor for each typeof equipment, we applied the following formula:EF (adjusted) = EF (steady state) * TAF * DFWhereEF (adjusted) = Final emission factor, adjusted fortransient operation and deterioration, g/hp-hrEF (steady state) = Steady-state emission factor, g/hp-hrTAF= Transient adjustment factor, unitlessDF = Deterioration factor, unitless= 1 + A * (cumulative hours * load factor)/median lifeat full load, in hoursA = Relative deterioration factor, unitless