new emissions-control technologies that benefit California and the rest of the nation.

EPA AND CARB TECHNICAL AND SCIENTIFIC PRACTICES IN SETTING STANDARDS

CARB and EPA have essentially the same starting point and motivation for setting new or stricter standards: attainment of the National Ambient Air Quality Standards (NAAQS). Each agency follows a series of procedural steps leading to a finalized regulation. These steps include identification of the need for new emissions standards, evaluation of potential control strategies, publication of proposed regulations, and solicitation of public comments on proposals before promulgating the regulations (Chapters 6 and 7). Some differences exist in the scope of CARB and EPA regulatory assessments as a result of the different procedures that the agencies must follow (Chapters 3, 6 and 7).

Recommendations

Consistent with a 2000 NRC report on modeling mobile-source emissions, CARB and EPA should work in tandem to improve mobile-source emissions models. In particular, consistent with this earlier NRC report, CARB and EPA should complete long-range plans that address improvements or new approaches to mobile-source emissions models. Such plans will improve estimations of emissions reductions. The estimations are a major part of assessing the impacts of emissions standards. The committee also recommends that CARB and EPA include, to the extent possible, air quality impact assessments as part of each rulemaking, because the effect of reducing mobile-source emissions on ambient pollutant concentrations will vary from region to region.

Although the committee did not have sufficient information to evaluate the safety issues associated with past regulations, it recommends that safety issues continue to be given careful consideration by EPA and CARB when setting mobile-source emissions standards.

Given that CARB and EPA emissions standards tend to require new technological developments, the committee also recommends that periodic assessments of technological feasibility be continued by the agencies for some of the more important standards. Examples of such stan-



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