(a) Except as otherwise provided under this section, the average fleet fuel economy for light-duty vehicles shall be increased by four percent per fiscal year, rounded to the nearest 1/10 mile per gallon, beginning November 21, 2009.

(b) Except as otherwise provided under this section, the average fleet fuel economy for medium-duty vehicles shall be increased by three percent per fiscal year, rounded to the nearest 1/10 mile per gallon, beginning November 21, 2009.

(c) Except as otherwise provided under this section, the average fleet fuel economy for heavy-duty vehicles shall be increased by two percent per fiscal year, rounded to the nearest 1/10 mile per gallon, beginning November 21, 2009.

(d) Notwithstanding the requirements of subsections (a), (b), and (c), the Green Fleets Review Committee may prescribe a lower average fuel economy percentage improvement for a specific fiscal year if the committee determines that the standards prescribed pursuant to subsections (a), (b), or (c) are neither of the following:

(1) Technologically achievable.

(2) Cost effective, as demonstrated by clear evidence.

(e) If a lower percentage fuel economy improvement is prescribed for a specific fiscal year under subsection (d), that percentage increase shall be the maximum increase that is both of the following:

(1) Technologically achievable.

(2) Cost effective.

(f) In determining cost effectiveness under this section, the committee shall take into account the total value to the nation of reduced petroleum use, including the value of reducing external costs of petroleum use, using a value for such costs equal to 25 percent of the value of a gallon of gasoline saved.

(g) In addition to determining cost effectiveness under this section, reducing harmful emissions and greenhouse gases created by the production and use of a fuel source shall be the second primary criteria taken into account by the committee. Whenever a fleet is taking into consideration a new fuel, the fuel provider shall submit U.S. Department of Energy statistics showing the life cycle emissions per gallon gasoline equivalent for the green fleet manager to submit to the committee.