68.—(1) Subject to regulation 72, this regulation applies to every wheeled vehicle first used on or after 1st April 1983 being an agricultural motor vehicle or an industrial tractor, other than—
(a)an agricultural motor vehicle which is first used on or after 1st June 1986 and which is driven at more than 20 mph; or
(b)a road roller.
(2) A vehicle to which this regulation applies shall be so constructed—
(a)that its sound level does not exceed—
(i)if it is a vehicle with engine power of less than 65 kw, 89dB(A);
(ii)if it is a vehicle with engine power of 65 kw or more, and first used before 1st October 1991, 92dB(A); or
(iii)if it is a vehicle with engine power of 65 kw or more, and first used on or after 1st October 1991, 89dB(A),
when measured under the conditions specified in paragraph 1.3 of Annex VI to Community Directive 74/151 by the method specified in paragraph 1.4.1 of that Annex using the apparatus prescribed in regulation 66(7); and
(b)that the device designed to reduce the exhaust noise meets the requirements specified in paragraph II.1 of that Annex and, if fibrous absorbent material is used, the requirements specified in paragraphs II.4.1 to II.4.3 of that Annex.