The In-Use Off-Road Diesel-Fueled Fleets Regulation (Off-road Regulation) was initially adopted in 2007 and applies to essentially all off-road vehicle operation in the state except agricultural, military, and personal use. Despite resistance from Associations representing the construction and mining industries, on November 17, 2022 the California Air Resources Board (CARB) adopted sweeping amendments to the Off-road Diesel Regulation. These amendments are expected to further reduce emissions from the operation of off-road diesel vehicles mainly by phasing out the oldest and dirtiest vehicles, those that are Tier 0, Tier 1 and Tier 2.