In this chapter, the following terms have the meanings indicated. Terms Defined. “Diesel vehicle” means a motor vehicle that: Is powered by a compression ignition engine; and Has a manufacturer's gross vehicle weight rating or gross combination weight rating over 10,000 pounds. “Governor” means a mechanism installed on a diesel engine by the original equipment manufacturer for the purpose of limiting the maximum engine speed. “Opacity” means the degree to which emissions reduce the transmission of light and obscure the view of an object in the background, expressed as a percent, as measured by emissions test equipment under Regulation .07 of this chapter. “SAE J1667” means the emissions test described in document number J1667 published by the Society of Automotive Engineers, entitled “Snap-Acceleration Smoke Test Procedure for Heavy-Duty Diesel Powered Vehicles,” which is incorporated by reference in Regulation .02 of this chapter. “State Police” means the Department of State Police.