Heavy-Duty Vehicle Inspection Program (HDVIP)
Heavy-Duty Vehicle Inspection Program (HDVIP) : This regulation authorizes random roadside smoke opacity testing of heavy-duty diesel trucks and buses. The opacity of exhaust emitted from these engines must not exceed 40 percent (1991 and newer engine model years) or 55 percent (all pre-1991 engines). Gasoline and diesel trucks and buses are also inspected for tampering and for engine certification label compliance.
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