(a) In addition to the provisions of section one hundred and forty-two J authorizing the department of environmental protection to establish and administer setting motor vehicle emissions standards, for model years beginning with the model year nineteen hundred and ninety-three or as soon thereafter as allowable under federal law, the department of environmental protection, hereinafter referred to as the department, shall adopt motor vehicle emissions standards based on the California's duly promulgated motor vehicle emissions standards of the state of California unless, after a public hearing, the department establishes, based on substantial evidence, that said emissions standards and a compliance program similar to the state of California's will not achieve, in the aggregate, greater motor vehicle pollution reductions than the federal standards and compliance program for any such model year. The department shall publicly issue detailed written findings before and after holding a public hearing pursuant to this paragraph and said hearing shall be subject to the provisions for public hearings contained in chapter thirty A. A decision not to adopt said standards shall apply as long as the federal standards and the standards of the state of California do not change. Emissions standards adopted pursuant to this section shall include the one hundred thousand mile certification standards of the state of California. Notwithstanding any other provision of this section, the department may postpone, for no more than one year, the adoption of said motor vehicle emission standards if the department makes a written determination that none of the following states is likely to adopt California's motor vehicle emission standards for model year nineteen hundred and ninety-three pursuant to the requirements of 42 USC 7507: Connecticut, Maine, New Hampshire, New Jersey, New York, Rhode Island, and Vermont. The department may further postpone adopting said motor vehicle emission standards for an additional year if the department makes a written determination that none of the aforesaid listed states is likely to adopt California's motor vehicle emission standards for model year nineteen hundred and ninety-four.