(a) The Commissioner may adopt rules necessary to implement the provisions of sections 1222, 1224, 1227, and 1228 of this title, relating to inspections and certification of inspection mechanics.(b) In consultation with the Secretary of Natural Resources or the Secretary's designee, the Commissioner shall adopt rules, pursuant to the provisions in 3 V.S.A. chapter 25, to establish a standard of exhaust-smoke emission for all diesel-powered commercial motor vehicles operated on the highways of this State. In establishing this standard, the Commissioner shall review standards in effect in other states and shall endeavor to maintain consistency with those standards. The rules adopted shall recognize different types and ages of vehicles and comprise standards that shall, at least in part, be based on the age of the vehicle. The standards shall be reviewed by the Commissioner periodically and may be revised in consultation with the Secretary of Natural Resources or the Secretary's designee, as the Commissioner deems appropriate. Additionally, the Commissioner, in consultation with the Secretary of Natural Resources or the Secretary's designee, shall adopt rules that select a method or methods for testing the exhaust emissions of diesel-powered commercial motor vehicles and that implement section 1222a of this title. The method selected shall be one that is designed to be performed without unreasonable delay for the vehicle being tested. The rules shall include a process by which the owner of a commercial motor vehicle may arrange with the Department of Motor Vehicles for the voluntary exhaust-smoke emission testing of a vehicle. For the purposes of this section, "commercial motor vehicle" is defined under subdivision 4103(4) of this title.Added 1997, No. 155 (Adj. Sess.), § 66l; amended 2005, No. 195 (Adj. Sess.) , § 1, eff. 5/26/2006.