Tech 4 Credit Model: Estimates for Emission Factors and Inspection and Maintenance Credits for 1981 and Later Vehicles for MOBILE3

摘要

The report provides the basis for the equations used in MOBILE3 to predict the emission levels of 1981 and newer gasoline powered light-duty passenger vehicles. This was done by characterizing the performance of vehicles in the Emission Factor data base separately for several technology types, such as fuel-injected versus carbureted, and recombining the technologies based on projected mixes to produce estimates of emissions of future model years. The Tech IV Credit Model is the computer software developed to calculate the MOBILE3 emission factor estimates. In addition, the model was used to estimate the emission reductions due to Inspection and Maintenance (I/M) programs for these vehicles. The emission levels of vehicles in the sample identified by various test type and cutpoint combinations were reduced to reflect repairs due to the I/M program. After combining the repaired and unrepaired vehicle emission levels, the overall reduction from the non-I/M base case is expressed as a fraction of the base case. This reduction fraction is scored in MOBILE3 and used to estimate fleetwide reductions due to I/M programs.