The provisions of sections 150.6, 150.7 and 150.8 of this Part shall not apply in the event of and for the duration of a valid certification to the Federal Highway Administration by the State in accordance with the terms of the agreement between the Commissioner of Transportation and the Secretary of Transportation of the United States, dated May 13, 1968. The regulations which have been promulgated for such areas with respect to size of signs, spacing of signs and lighting in commercial and industrial zones shall control. For the purposes of this section, requirements as to the number of signs permitted on a single plot or parcel of land will be considered to be a spacing requirement.