CARB: Diesel vehicle emission programs

Scope

This regulation applies to vehicle owners that operate diesel powered vehicles.

Regulatory citations

• Title 40 Code of Federal Regulations
• Title 13 and Title 17 of the California Code of Regulations

Key definitions

• California Air Resources Board (CARB): The state agency in California charged with controlling air pollution.
• Carbon dioxide: A gaseous exhaust from an internal combustion engine that is damaging to the atmosphere.
• United States Environmental Protection Agency (EPA): The federal agency charged with enforcing the Clean Air Act.
• Nitrogen Oxides (NOx): Nitrogen dioxide and other gaseous exhaust from an internal combustion engine that are damaging to the atmosphere.
• Particulate matter (PM), also known as diesel particulate matter: The solid emissions released by a diesel-powered vehicle. Can also be referred to as diesel soot. It is the black exhaust older diesel vehicles release.

Summary of requirements

U.S. EPA

The Environmental Protection Agency (EPA) has traditionally:

• Placed emissions limits on vehicle emissions that manufacturers must meet, and
• Enforced rules that make it illegal to tamper with the emissions systems on vehicles.

The emissions limits placed on diesel power vehicles over the years (since the 1990s) have required a reduction in PM emissions, NOx emissions, and CO2 emissions. Major changes in the limits and their impact were:

• 2007: The required reduction in PM emissions (PM emissions were limited to 0.25g/bhp-hr) lead to the installation of the diesel particulate filters on the majority of diesel-powered vehicles.
• 2010: The required reduction in specific gases (NOx limited to 1.2g/bhp-hr based on the manufacturer’s fleet average) lead to the installation of selective catalytic reduction (SCR) systems on the majority of diesel-powered vehicles. These systems inject diesel exhaust fluid (DPF) into the exhaust stream, resulting in the NOx being broken into nitrogen and water.

Under the legacy EPA rules, a vehicle must meet the emissions standards that were in place the year the engine was manufactured and have all of the emissions control components on it that were required the year the vehicle was manufactured.

The Environmental Protection Agency (EPA) Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards rule was finalized in 2022. These regulations:

• Apply to the manufacturers of on-highway heavy-duty trucks and engines, and
• Implement more stringent emissions standards over a wider range of operational conditions.

Implementation begins with model year (MY) 2027.

Technically, this is the first rule in EPA's Clean Truck Plan. The second was the more stringent emissions standards for light and medium duty trucks, and the third is the rule below (GHG Emissions Standards for Heavy-Duty Vehicles - Phase 3).

The recently passed EPA Greenhouse Gas Emissions Phase 3 final rules are emissions standards new vehicles must meet. The regulations apply to the manufacturers of on-highway heavy-duty trucks. Reductions in emission required under this rulemaking does not start for day cabs until MY 2028. As of MY 2028, manufacturers must reduce greenhouse gas emissions across their day cab offerings by 8%. That increases annually until 2032, by which time the manufacturers must have decrease greenhouse gas emissions across their day cab offerings by 40 percent. Sleeper cab tractors have a delayed timeline.

CARB

The California Air Resources Board (CARB) regulates air emissions in California. It has several long-standing programs in place and three newer programs. Advanced Clean Truck (ACT): Under this rule, manufacturers must sell a specific percentage of zero emissions vehicles (ZEVs) to be able to sell vehicles in California. Other states are or will be adopting regulations similar to CARB’s ACT.

Advanced Clean Fleet (ACF): Under this rule, drayage trucks, high priority fleets, and government fleets must register their California fleet (vehicles used in California) in CARB’s TRUCRS system. This program requires covered fleets to begin replacing the internal combustion engine (ICE) units used in their California fleet with zero emissions vehicles (ZEVs) over time High priority fleets under the ACF program are fleets that operate vehicles with a GVWR of 8,501 pounds or more in California and have:

• 50 or more covered vehicles operating in California, or
• One covered vehicle operating in California and an annual revenue of $50 million or more.

Clean Truck Check (CTC) (also known as the HD I/M regulations): This program requires all non-gasoline powered ICE vehicles that operate in California with a GVWR of 14,001 pounds or more to be registered in CARB’s CTC-VIS database. Part of registering includes paying a $30 per vehicle annual compliance fee. This program also requires vehicle owners or operators to upload onboard diagnostic (OBD) downloads twice a year to CARB proving that the vehicle is operating within its designed emissions parameters. The OBD download/upload must be done by a CARB licensed HD I/M tester. Becoming a licensed tester involves taking a CARB training class, passing the final exam, and acquiring the approved equipment.

Truck and Bus regulation: This requires all vehicles diesel-powered vehicles with a GVWR of 14,001 pounds to have a MY 2010 or newer engine.

Greenhouse Gas Reduction: This program requires van-type trailers that are over 50 feet in length and the tractors pulling them to have full aerodynamics and low rolling resistance tires.

Drayage Truck regulation: All trucks that operate into, out of, and inside of rail ramps and ports (called drayage trucks) must be registered in the CARB Drayage Truck database and be equipped with a 2010 or newer engine. These trucks are also subject to ACF requirements starting in 2024.

Periodic Smoke Inspection Program (PSIP): This regulation requires fleet owners/operators to have their California-based diesel-powered vehicles with a GVWR of 6,001 pounds or more to undergo an annual smoke opacity test once the vehicle reaches four years old (based on model year). This program will remain in place until the Clean Truck Check program is fully implemented in 2025.

Transport Refrigeration Unit (TRU) regulations: To operate in California, a diesel-powered TRU must meet the ULETRU emissions standards, be registered in CARB’s ARBER database, and display an ARB-assigned ID number. TRUs from model year 2023 and newer must meet the next round of PM standards and use Lower Global Warming Refrigerant. Starting in 2024, fleets that use truck mounted reefers (TRUs on straight trucks), must begin transitioning away from diesel reefers and to zero-emissions reefers.