The amendments will require fleets to phase-out use of the oldest and highest polluting off-road diesel vehicles in California; prohibit the addition of high-emitting vehicles to a fleet; and require the use of R99 or R100 renewable diesel in off-road diesel vehicles. These vehicles are the second largest mobile source of NOx in California, only exceeded by trucks on roads and highways, aka on-road trucks.

Off-road vehicles covered by the amendments are used in construction, mining, industrial operations, and other industries. The amendments phase-in starts in 2024 through the end of 2036. They include changes to improve enforceability and encourage the adoption of zero-emission technologies. CARB initially adopted the Off-Road Regulation in 2007 and approved amendments in 2009 and 2010.