40 C.F.R. § 202.22 Visual exhaust system inspection.
Title 40 - Protection of Environment
No motor carrier subject to these regulations shall operate any motor vehicle of a type to which this regulation is applicable unless the exhaust system of such vehicle is (a) free from defects which affect sound reduction; (b) equipped with a muffler or other noise dissipative device; and (c) not equipped with any cut-out, bypass, or similar device.
Title 40: Protection of Environment
PART 202—MOTOR CARRIERS ENGAGED IN INTERSTATE COMMERCE
Subpart B—Interstate Motor Carrier Operations Standards
§ 202.22 Visual exhaust system inspection.