(1) The term "passenger automobile" means any four wheeled vehicle propelled by fuel which is manufactured for use on public streets, roads and highways, which is rated at six thousand pounds gross vehicle weight or less, and which the commissioner determines by rule is manufactured primarily for use in the transportation of not more than ten individuals.

(2) The term "passenger automobile" shall not include police, fire, or other emergency vehicles, as defined by the commissioner, or snow removal, salt-spreader, and garbage disposal vehicles, or any vehicles which the commissioner determines, by regulation, should be excluded from being defined as "passenger vehicles".

(3) The term "average fuel economy" means the total number of passenger automobiles acquired in a fiscal year to which this section applies divided by a sum of terms, each term of which is a fraction created by dividing (i) the number of passenger automobiles so acquired of a given model type, by (ii) the rated fuel economy of such model type as determined and published by the federal agency with jurisdiction over the determination and publication of such fuel economy ratings during that fiscal year.

(4) The term "average fuel economy standard" means the average miles per gallon to be achieved in the operation of passenger automobiles manufactured in a particular model year and shall be as follows: Model year Fuel economy standard