Maricopa County Advances in Efforts to Lower Vehicle Emissions
Maricopa County is making strides towards securing federal approval for its innovative rules designed to incentivize lower vehicle emissions. The county is awaiting the Environmental Protection Agency’s (EPA) final green light for two key regulations that aim to reduce air pollution by providing credits for upgrading or replacing high-emission vehicles.
These regulations, known as Rule 204 and Rule 205, have already been approved locally but require EPA endorsement to take effect. The rules allow companies to purchase credits to offset their emissions and comply with the federal Clean Air Act requirements.
“They’re in effect but they’re really not effective in terms of creating ERCs [credits],” explained Maricopa County Air Quality Director Philip McNeely.
EPA Administrator Lee Zeldin recently visited Arizona to commend Maricopa County on its proactive measures. Zeldin stated, “They aren’t increasing emissions and they aren’t breaking federal requirements, they’re finding new innovative ways to work within their circumstances.”
The EPA has given its proposed approval to Rule 204 just last week, following an earlier nod to Rule 205 in April. Rule 205 pertains to on-road vehicles such as trucks, whereas Rule 204 addresses off-road vehicles like tractors and excavators.
The latest revisions for Rule 205 were made in May 2025, while Rule 204 saw updates in November 2025. These rules will enter a 30-day public comment period after the proposed approval, post which the EPA will review comments before deciding on final approval.
During public remarks last week, Maricopa County Board of Supervisors Chair Kate Brophy McGee emphasized, “It is possible to do what is being proposed with Rule 204 and maintain the quality of life, maintain what we value here in Maricopa County, and support and drive the robust economic development that we are undergoing.”
