California to adopt regulations on NOx emissions

California has adopted EPA emissions standards, is in the process of adopting Omnibus Low NOx regulations that would set lower engine Nitrogen Oxides (NOx) emissions standards in both 2024 and 2027, and is taking additional steps to extend the warranty periods and adopt stricter initial testing and compliance requirements.

California is also in the process of establishing the Advanced Clean Trucks rule, a mandate that requires manufacturers of medium and heavy-duty vehicles to sell an increasing minimum percentage of zero-emission vehicles from 2024 to 2035.


In 2008, the California State Air Resources Board (ARB) approved the Heavy Vehicle GHG Emissions Reduction Regulations in an effort to reduce GHG emissions from certain long-haul trucks operating in California by requiring them to use technologies that improve fuel efficiency (regardless of where the vehicle is registered).

The regulation, which took effect in 2010, required owners of long-haul tractors and 53-foot trailers to be EPA SmartWay certified or to replace or modernize their vehicles with aerodynamic technologies and low-rolling resistance tires.

In addition, the regulation contained certain registration and emission standards for refrigerated trailers.

Then, in February 2018, the California ARB approved the California Phase 2 standards that generally align with the federal Phase 2 standards, with some minor additional requirements, and which would remain in effect even if the federal standards of the Phase 2 are affected by the action of President Trump’s administration.

Thus, in February 2019, the California Phase 2 standards became final.


In June 2020, the ARB passed the Advanced Clean Trucks (ACT) regulation, which requires original equipment manufacturers to begin shifting toward increased production of zero-emission heavy-duty tractors beginning in 2024.

According to ACT, by 2045, every new tractor sold in California will have to be zero-emission.

While ACT does not apply to those who simply operate tractors in California, it could affect the cost and / or supply of traditional diesel tractors and may lead to similar legislation in other states or at the federal level.

Overall, the Advanced Clean Trucks regulation requires manufacturers to sell an increasing proportion of zero-emission trucks, vans, and electric vans beginning in 2024.

By 2045, the Advanced Clean Trucks regulation seeks to make every new commercial vehicle sold in California zero emissions.

Additionally, in September 2020, the Governor of the State of California issued an executive order establishing the following California goals:

100% of the state’s sales of new passenger cars and trucks will be zero emissions by 2035.

100% of medium and heavy duty vehicles in California will be zero emissions by 2045 for all operations, where feasible, and by 2035 for haul trucks.

The state will also transition to 100% zero-emission off-road vehicles and equipment by 2035 when possible.

Likewise, the Executive Order of September 2020 directed CARB to develop and propose regulations and strategies aimed at achieving the above objectives.


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