Notice to California fleets: If you haven’t been following the bus and truck regulations coming into effect at the beginning of each New Year, you might be in for a surprise — and a hefty dent in your budget.

The rules, as drafted by the California Air Resources Board (ARB), are designed to reduce emissions by bringing older heavy-duty diesel trucks in commercial fleets up to the cleaner 2010 engine standards. While there are separate requirements for heavy-duty Class 7 and 8 trucks, this discussion will concentrate on diesel trucks in the GVWR range of 14,000 lbs. to 26,000 lbs.

California fleets must comply with a schedule that requires replacement of engines 20 years and older. Therefore, as of Jan. 1, 2015, trucks in this GVWR range with 1995 engines or older must be replaced with trucks using 2010 engines or newer. A year from now, trucks with 1996 engines or older must be replaced, and so on. Starting January 1, 2020 — if you can think that far ahead — all remaining trucks would need to be replaced with 2010 model-year engines or equivalent emissions by 2023.

Heavy-duty trucks can comply with retrofit diesel particulate filters (DPFs); not so for the lighter trucks because their upgrade requirements were delayed. The regulations are based on engine year, not model year, so affected trucks must undergo an entire engine replacement. In all practicality, that means replacing the truck.

But before you get rid of your old trucks and buy new(er) ones, understand the exceptions, as they can provide extra time to comply with the rules or even exempt your vehicles entirely.

First, you can delay phase-in if your affected trucks operate solely in the cleaner NOx exempt areas as designated by ARB (mainly NorCal and Central Coast counties).

Fleets can also take advantage of the “Low Mileage Work Truck Phase-In Option,” which allows for a delayed installation of DPF vehicles that travel fewer than 20,000 miles per year. You’d need to report your odometer readings to CARB to take advantage. This option also depends on the percentage of trucks in your fleet that comply with the DPF requirements.

In terms of an outright exemption, if your older trucks travel fewer than 5,000 miles per year total (or 1,000 miles per year in California for out-of-state fleets), then you can claim the “Low-Use Exemption” by reporting your odometer readings.

There are other extensions for specific fleet applications and economic hardship. Fleets have until Jan. 31 to file to take advantage of these “flexibility options.”

If you’ve had your head in the sand, these regulations might be taking you off guard. But they shouldn’t be — the initial regulations were announced in 2008.

With proper reporting, fleets can get creative to comply with the rules, says Beth White, the manager that oversees the implementation of the truck and bus regulations for ARB. For instance, fleets can assign older trucks to low-mileage routes to satisfy the low-mileage extension or low-use exemption. Fleets that need to replace could buy used vehicles. A truck with a 2007 diesel engine isn’t due for replacement until 2023, for instance. “Depending on the cost of the truck that’s an option that a lot of people are taking,” White says.

In terms of rules enforcement, CARB has its own enforcement division, according to White. In coordination with the California Highway Patrol, trucks can be checked at border crossings, weigh stations, truck stops and ports and issued a citation for non-compliance.

For fleets outside of California, you might be thinking, “I’m glad I don’t operate in California. But I will buy one of your used trucks.”

We don’t have enough room here to fully explain the regulation details, including the vehicles affected, percentage requirements, extensions and exemptions. Visit www.arb.ca.gov/dieseltruck for details, or call 866-634-3735.