Massachusetts Truck Emissions & Clean-Truck Rules

How Massachusetts handles truck emissions

Massachusetts tests heavy diesel smoke, but only on its own plates. A medium- or heavy-duty diesel at 10,001 lb GVWR or more, model year 1984 or newer, that is not equipped with an OBD system must pass an annual opacity test as part of the Massachusetts Vehicle Check inspection, alongside the annual commercial motor vehicle inspection for everything over 10,000 lb GVWR. An out-of-state rig rolling through is not enrolled. The Advanced Clean Trucks rule (310 CMR 7.40) binds manufacturers, and MassDEP granted enforcement discretion for model years 2025 and 2026, with full compliance from 2027. Keep your DPF and DEF working; federal tampering penalties run about $45,000 per engine.

What applies to you

• Program: Clean Truck Check
• State rule: 10,001 lb GVWR is the line for the Massachusetts opacity test. A medium- or heavy-duty diesel at or above it, model year 1984 and newer, that is not equipped with an OBD system must pass an annual smoke opacity test as part of its Massachusetts Vehicle Check inspection, and all heavy-duty motor vehicles over 10,000 lb GVWR also take the annual commercial motor vehicle inspection. Both apply to Massachusetts-registered vehicles, not to a truck passing through. Massachusetts also adopted the Advanced Clean Trucks rule (310 CMR 7.40), a manufacturer sales mandate, with MassDEP enforcement discretion for Class 2b-8 vehicles for model years 2025 and 2026 as long as makers keep supplying internal-combustion trucks without restriction, and full compliance from model year 2027. Federal EPA standards otherwise apply.
• Penalty: No state emissions fine binds an out-of-state driver; ACT non-compliance penalties fall on manufacturers. Federal EPA anti-tampering penalties apply: about $45,000 per tampered engine and about $4,500 per defeat device sold or installed.
• DPF / DEF: Federal EPA equipment nationwide, never delete or tamper with it

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