(a) Exhaust emissions from new 1973 and 1974 model-year diesel-powered engines for use in heavy-duty motor vehicles (6,001 pounds and over, manufacturer's maximum gross vehicle weight) shall not exceed:

(b) Exhaust emissions from new 1975 and 1976 model-year diesel powered engines for use in heavy-duty motor vehicles (over 6,000 pounds, manufacturer's maximum gross vehicle weight) shall not exceed:

The test procedures for determining compliance with these standards are those set forth in “California Exhaust Emission Standards, Test and Approval Procedures for 1975 and Subsequent Model-Year Engines in Diesel-Powered Motor Vehicles Over 6,000 Pounds Gross Vehicle Weight,” dated December 19, 1973, amended August 8, 1974.

(c) Exhaust emissions from new 1977 model year diesel-powered engines for use in heavy-duty motor vehicles shall not exceed:

These two sets of standards shall be alternatives. A manufacturer shall have the option for each engine family of showing compliance with either set.

The test procedures for determining compliance with these standards are those set forth in “California Exhaust Emission Standards and Test Procedures for 1975 and Subsequent Model-Year Diesel-Fueled Heavy-Duty Engines and Vehicles,” dated December 19, 1973, as last amended March 31, 1976.

(d) Exhaust emissions from new 1978 model-year diesel-fueled heavy-duty engines and vehicles, except medium-duty vehicles, shall not exceed:

These two sets of standards shall be alternatives. A manufacturer shall have the option for each engine family of showing compliance with either set.

The test procedures for determining compliance with these standards are those set forth in “California Exhaust Emission Standards and Test Procedures for 1975 to 1978 Model-Year Diesel-Fueled Heavy-Duty Engines and Vehicles,” dated December 19, 1973, as last amended October 5, 1976.

A manufacturer may elect to certify heavy-duty vehicles less than 10,000 pounds maximum gross vehicle weight rating as medium-duty vehicles under Section 1959 of this chapter, in which event heavy-duty emission standards and test procedures shall not apply.

(e) This regulation shall remain in effect until December 31, 1988, and as of that date is repealed unless a later regulation deletes or extends that date. Notwithstanding the repeal or expiration of this regulation on December 31, 1988, the provisions of the regulation as they existed prior to such repeal or expiration shall continue to be operative and effective for those events occurring prior to the repeal or expiration.