DEC warns Vermont senators EPA approval, modeling needed before changing annual emissions inspections

Rachel Stevens, an attorney for the Agency of Natural Resources, told the Senate Transportation Committee that a proposed change to Vermont's vehicle emissions inspection schedule would face legal and technical hurdles and could increase air pollution.

Stevens, joined by Deirdre Ritzer of the Department of Environmental Conservation's Air Quality and Climate Division, said federal law requires new motor vehicles to comply with emissions standards and that Vermont follows California's low-emission vehicle rules. "All new motor vehicles, regardless of whether it's purchased or it's built at home, must comply with the latest emissions standards," Stevens said.

Why this matters: S.211 would alter the annual inspection requirement that applies to light-duty vehicles; DEC said moving to a biennial schedule would likely increase emissions of ozone precursors, nitrogen oxides, particulate matter and carbon monoxide because delays between inspections allow malfunctioning equipment to operate longer. Stevens said, "If a vehicle's check engine light is illuminated, this means the manufacturer has already determined that the emissions have increased by 50 or more," and used that example to illustrate the risk of deferred repairs.

Legal and procedural constraints: DEC emphasized that federal Clean Air Act requirements and EPA regulations set a performance standard the state must meet. Stevens said Vermont would need to demonstrate that a biennial inspection program meets the EPA performance standard through emissions modeling and would have to amend its State Implementation Plan (SIP) and obtain EPA approval before any change could take effect. She cited a recent federal district court decision in New Hampshire as a cautionary precedent underscoring that federal oversight matters when states change inspection programs.

Data and trade-offs: Agency staff provided inspection data to the committee: in 2025 there were 13,880 emissions failures in roughly 383,000 emissions inspections, with total inspections approaching 500,000; the agency estimated emissions failures were in the neighborhood of 4 percent of emissions inspections. DEC staff also noted that in other jurisdictions 28 states plus DC require emissions inspections, with 11 jurisdictions on annual inspections, 13 on biennial schedules and five using mixed approaches depending on vehicle age.

Committee response and research request: Several senators pushed back on DEC's assumption that fewer inspections cause fewer repairs. One senator (Speaker 5) cited research suggesting that affordability, access to repair shops and vehicle downtime drive repair timing and asked DEC for more analysis. The senator said the evidence he had reviewed showed little connection between inspection frequency and whether people obtain repairs.

Next steps: Stevens told the committee that modeling could probably be done in a matter of weeks (she estimated roughly two to three weeks of staff time) but that EPA approval is the critical limiting factor. The committee asked DEC to coordinate with DMV and VTrans, to produce modeling and timing estimates, and to return with more detailed information; members discussed setting an effective date that accounts for the time needed for SIP amendment and EPA review.