California Agricultural Diesel Truck Regulations Adopted

Last year I wrote about new regulations proposed by the California Air Resources Board (CARB) to control exhaust emissions from diesel engines. The requirements in the draft regulations covered diesel engines used in trucks and off-the-road applications. It was estimated that the rules would affect almost a million trucks used in the state and thousands of diesels engines used in off-the-road vehicles, such as farm tractors. Estimates were that California growers would have to replace or retrofit as many as 400,000 trucks and tens of thousands of older diesel agricultural tractors.


The problem for California agriculture is that many diesel trucks are used for only a few months of the year, usually during harvest season, and operate less than 15,000 miles per year, while an over-the-highway truck may operate 150,000 thousand miles per year. Thus, many trucks used in California agriculture are 10 to 15 or more years old and would have to be retrofitted or replaced.

Meeting Requirements

These draft regulations were part of CARB’s efforts to meet requirements of the Federal Clean Air Act. Although the draft regulations allowed for retrofitting older trucks and exempted trucks operating less than 7,500 miles per year, many older trucks could not be practically retrofitted and the mileage exemption was too low for most diesel trucks used by California growers.

Needless to say, the cost of meeting these new regulations would have placed a tremendous economic burden on California growers, and many California agricultural organizations protested the draft regulations. California Farm Bureau even surveyed its members on diesel truck usage and sent this information to CARB to help the agency understand the problems the regulations would create for California growers.

In December, CARB announced final diesel truck emission rules that gave additional time to comply with the rules for limited-use diesel vehicles. Under the new regulations, trucks with pre-1966 model engines would be exempt from the new regulations until Jan. 1, 2017, if they were used for less than 15,000 miles per year.

For trucks with newer model engines, the annual mileage would go up. For example, for 1996 through 2005 model engines, the mileage limit would be less than 20,000 miles. Low mileage agricultural vehicles with less than 10,000 miles per year use would be exempt until Jan. 1, 2023. These final regulations will allow for a longer transition period and for agricultural truck owners to plan and budget for truck updates to meet the CARB requirements.

Although the final regulations for trucks have made it easier for California agriculture, the final regulations for off-the-road diesel engines have not yet been issued. California growers still do not know if they will have to replace tens of thousands of older farm tractors which will not meet the draft off-the-road standards.