PUBLIC LAW 101-549—NOV. 15, 1990 104 STAT. 2479 taking costs, energy, and safety into account. Any revised standard shall require a reduction of emissions from the standard that was previously applicable. Any such revision under this title may provide for a phase-in of the standard. It is the intent of Congress that the numerical emission standards specified in subsections (a)(3)(B)(ii), (g), (h), and (i) shall not be modified by the Administrator after the enactment of the Clean Air Act Amendments of 1990 for any model year before the model year 2004.". (d) PROMULGATION.—Section 202(b)(2) of the Clean Air Act (42 U.S.C. 7521(b)(2)) is amended to read as follows: "(2) Emission standards under paragraph (1), and measurement Regulations, techniques on which such standards are based (if not promulgated prior to the date of the enactment of the Clean Air Act Amendments of 1990), shall be promulgated by regulation within 180 days after such date.". SEC. 204. CARBON MONOXIDE EMISSIONS AT COLD TEMPERATURES. Section 202 of the Clean Air Act (42 U.S.C. 7521) is amended by adding the following new subsection after subsection (i): "(j) COLD CO STANDARD. — "(1) PHASE I. —Not later than 12 months after the date of the Regulations, enactment of the Clean Air Act Amendments of 1990, the Administrator shall promulgate regulations under subsection (a) of this section applicable to emissions of carbon monoxide from 1994 and later model year light-duty vehicles and lightduty trucks when operated at 20 degrees Fahrenheit. The regulations shall contain standards which provide that emissions of carbon monoxide from a manufacturer's vehicles when operated at 20 degrees Fahrenheit may not exceed, in the case of lightduty vehicles, 10.0 grams per mile, and in the case of light-duty trucks, a level comparable in stringency to the standard applicable to light-duty vehicles. The standards shall take effect Effective date, after model year 1993 according to a phase-in schedule which requires a percentage of each manufacturer's sales volume of light-duty vehicles and light-duty trucks to comply with applicable standards after model year 1993. The percentage shall be as specified in the following table: "P HASE-IN SCHEDULE FOR COLD START STANDARDS 1994 1995 1996 and after Model Year Percentage 40 80 100 "(2) PHASE IL—(A) Not later than June 1, 1997, the Administrator shall complete a study assessing the need for further reductions in emissions of carbon monoxide and the meiximum reductions in such emissions achievable from model year 2001 and later model year light-duty vehicles and light-duty trucks when operated at 20 degrees Fahrenheit. "(B)(i) If as of June 1, 1997, 6 or more nonattainment areas have a carbon monoxide design value of 9.5 ppm or greater, the regulations under subsection (a)(1) of this section applicable to emissions of carbon monoxide from model year 2002 and later
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