EMISSION BENEFITS OF VEHICLES THAT SATISFY ZEV PROGRAM
Section 4 examines the incremental costs of the various types of vehicles that may be produced to satisfy the ZEV program requirements. This section examines what these additional costs will buy in terms of emission reductions. As we did with costs, we calculate emission reductions relative to a vehicle that meets the super ultra low emission vehicle (SULEV) exhaust standard and the near-zero evaporative emission standard. This is the cleanest vehicle required under CARB regulations outside the ZEV program.
Motor vehicle emissions can be divided into three categories: tailpipe (or exhaust), evaporative, and indirect (or fuel-cycle). For each, we present estimates of the emission rates in grams per mile for the different advanced technology vehicle categories created by the ZEV program.
Tailpipe, or exhaust, emissions include those occurring during vehicle start-up and warm- up and during operation at running temperature. Our estimates of tailpipe emission rates are taken from CARB's analysis of vehicle emissions using its most recent emission model— EMFAC2000 (CARB, 2000b, pp. 134–137). Table 5.1 lists average lifetime emissions for the advanced technology vehicles: the partial zero emission vehicle (PZEV); the advanced technology PZEV (ATPZEV), which in this case is a gasoline hybrid electric vehicle (GHEV); and the battery-powered electric vehicle (BPEV). The first set of rows in the table reports CARB's estimated average rates of tailpipe emissions in grams per mile over the life of the vehicle. Though not explicitly stated in CARB's write-up, these estimates are probably averages over the vehicle's “useful life, ” which CARB defines as 10 years and 120,000 miles (CARB, 2001g, p. C-1). As discussed in Subsection 4.4, average life and miles traveled are likely longer. CARB's emission rates assume different emission control system deterioration rates over the life of the vehicle. The second column of Table 5.1 lists emission rates with a high deterioration rate; the third column lists those with the standard deterioration rate used in past analyses. We use the higher rate for our estimate of SULEV emissions because emission rates based on the standard deterioration rates likely understate emissions over the full life of the vehicle.