The emission standards adopted by the state board pursuant to

Section for the and later model-year motor vehicles shall be limited by the following: (

a) For all gasoline-powered passenger vehicles prior to the model year, the state board shall not adopt primary standards for the emission of oxides of nitrogen which are more stringent than 0.7 grams per vehicle mile, unless the state board by regulation also provides for optional standards which are not more stringent, with respect to each constituent, than 0.39 grams per vehicle mile for nonmethane hydrocarbon, 7.0 grams per vehicle mile for carbon monoxide, and 0.7 grams per vehicle mile for oxides of nitrogen.

For gasoline-powered light-duty vehicles and medium-duty vehicles prior to the model year of less than 4,000 pounds unladen weight, the state board shall not adopt primary standards for the emission of oxides of nitrogen which are more stringent than 1.0 gram per vehicle mile, unless the state board by regulation also provides for optional standards which are not more stringent, with respect to each constituent, than 0.39 grams per vehicle mile for nonmethane hydrocarbon, 9.0 grams per vehicle mile for carbon monoxide, and 1.0 gram per vehicle mile for oxides of nitrogen.

Any option may not impose certification, warranty, or enforcement requirements of greater duration or stringency than those set forth in the regulations applicable to and later model years, as adopted or amended by the state board on May 20, 1981. (

b) If the state board intends by regulation to eliminate for and later model-year vehicles the optional standards specified in subdivision (a), the state board shall submit to the Legislature, not later than January 15th of the year which is at least two calendar years prior to the year in which production would commence of vehicles subject to the new standard, a report with an estimate of the air quality benefits of the more stringent standard, the technological and economic feasibility of requiring the standard, and the potential effects on fuel economy associated with the standard.

The state board shall consult with the Environmental Protection Agency and motor vehicle and engine manufacturers prior to submitting the air quality and fuel economy estimates.