Technical standards

Applicability and exceptions

The affected medium- and heavy-duty fleet incorporates all on-road vehicles rated at a GVW ≥ 8,500 lbs. and the engines that power them, except those covered by the GHG emissions and Corporate Average Fuel Economy (CAFE) standards for MYs 2012–2016 light-duty vehicles. CO₂ and fuel consumption standards are applicable to the following categories of vehicles:

Most vehicles covered by the regulation carry payloads of goods or equipment, in addition to passengers. To account for this in the regulatory program, two types of standard metrics have been adopted:

1. Gram CO₂per ton-mile (and gallon of fuel per 1,000 ton-mile) standards for vocational vehicles and combination tractors
2. Gram CO₂ per mile (and gallon of fuel per 100-mile) standards for pickups and vans

CO₂ and fuel consumption standards

EPA and NHTSA have joint final standards for the three main heavy-duty regulatory categories: combination tractors, heavy-duty pickup trucks and vans, and vocational trucks.

Combination tractors

Differentiated standards were adopted for nine subcategories of combination tractors based on three attributes: weight class, cab type, and roof height. Phase 1 and Phase 2 final standards are shown below. Phase 2 added standards for Class 8 Heavy Haul Tractors, which are heavier than 120,000 lbs.

The regulation also defines two sets of standards for tractor engines for MYs 2021, 2024, 2027, and beyond: (1) CO₂ standards and (2) fuel consumption standards. Engine-based standards must be met by heavy-heavy-duty (HHD) and medium-heavy-duty (MHD) diesel engines used in combination tractors. If manufacturers met the MY 2021 standards a year earlier for MY 2020, their MYs 2024–2026 standards were slightly relaxed, but they are still required to meet the MY 2027 standards for MY 2027.

Heavy-duty pickup trucks and vans

These vehicles must meet CO₂ and fuel economy standards in an approach similar to that taken for light-duty vehicles, but with different standards for gasoline and diesel vehicles. EPA has established CO₂ standards in the form of target standard curves, based on a “work factor” that combines a vehicle’s payload, towing capabilities, and whether it has 4-wheel drive. The Phase 2 standards will phase in with increasing stringency in each MY from 2021 to 2027, requiring 16% CO₂ emissions reduction by MY 2027 compared to MY 2017 baselines. The EPA standards include a separate standard to control air conditioning system leakage. NHTSA has set corporate average standards for fuel consumption that are equivalent to EPA’s standards (but does not include EPA’s air conditioning leakage standard).

Both agencies provide manufacturers with two alternative phase-in approaches. One approach phases the final standards in at 15-20-40-60-100 percent in model years 2014-2015-2016-2017-2018. The other phases the final standards in at 15-20-67-67-67-100 percent in MYs 2014-2015-2016-2017-2018-2019.

Vocational trucks

This vehicle segment has been divided into 18 regulatory subcategories based on fuel type (diesel or gasoline), weight class (light, medium, and heavy), and duty cycle (urban, multi-purpose, and regional). As with tractor trucks, there are per-vehicle fuel efficiency and greenhouse gas requirements in MYs 2021, 2024, and 2027.

Engine standards for light heavy-duty (LHD), medium heavy-duty (MHD), heavy heavy-duty (HHD) diesel engines and for heavy-duty gasoline engines up to MY 2027 are shown below.

Trailers

Phase 2 includes the first CO₂ emission and fuel efficiency standards for trailers hauled by Class 7 and 8 tractor trucks. The original standards were finalized for MYs 2018, 2021, 2024, and 2027.  Since 2017, there has been a court-ordered stay on the enforcement of these trailer standards, and the legal challenge has not yet been resolved.

The standards for box-type trailers entail a bin system of aerodynamic bins numbered I–VIII to certify new trailers. Manufacturers will have to switch to higher numbered bins over time. Other compliance technologies include low resistance rolling tires, automatic tire inflation systems, and trailer weight reduction. Final MY 2027 trailer requirements are shown below:

Testing

The requirements for tractors and vocational vehicles include both engine and vehicle standards. Engine manufacturers are subject to the engine standards. Testing is conducted over one test cycle:

• Tractor engines are tested over the steady-state Supplemental Emissions Test (SET)
• Vocational engines are tested over the Federal Test Procedure (FTP) transient test
• Heavy-duty pickups and vans are tested over the light-duty FTP and the Highway Federal Economy Test

Chassis manufacturers are subject to the vehicle standards. Compliance for tractor trucks and vocational vehicles is determined based on a vehicle simulation model, called the Greenhouse gas Emission Model (GEM), which was developed by the EPA as part of the Phase 1 regulatory development process and has been subsequently updated several times, including as part of the Phase 2 rulemaking. The regulation does not require chassis dynamometer testing due to the large variety of vehicle configurations and the scarcity of heavy-duty chassis dynamometer test facilities.

Instead of using a chassis dynamometer as a way to evaluate real-world operation and performance, various characteristics of the vehicle are measured, and these measurements are used as inputs to GEM. These characteristics relate to key technologies applicable to a given truck category. This includes inputs such as engine- and transmission-specific data, aerodynamic performance, weight reduction, tire rolling resistance, the presence of idle-reducing technology, and vehicle speed limiters.

Useful life

EPA CO₂ emissions must be met over the engine and vehicle’s useful life. The useful life definitions for engines and vehicles that use the respective engine categories were identical to those defined for criteria pollutant standards for MY 2004 and later heavy-duty engines in the Phase 1 regulation. The Phase 2 standards increased the useful life for LHDDE only for GHG emissions, not criteria pollutant standards. Useful life is measured either in miles driven or years of use, whichever comes first:

• LHDDE and commercial pickup trucks and vans: 150,000 miles or 5 years
• MHDDE: 185,000 miles or 10 years
• HHDDE: 435,000 miles or 10 years

Other standards and provisions

N₂O and CH₄ standards

N₂O and CH₄ standards introduce emission standards for nitrous oxide and methane:

• Engine testing (tractors & vocational): N₂O = 0.10 g/bhp-hr; CH₄ = 0.10 g/bhp-hr
• Chassis testing (pick-ups and vans, FTP-75 & HWFET): N₂O = 0.05 g/mi; CH₄ = 0.05 g/mi

Testing requirements start from MY 2015 and are consistent with N₂O and CH₄ requirements for light-duty vehicles. The standards were designed to cap emissions at current levels to prevent N₂O and CH₄ emission increases in future engines.

A/C leakage

EPA adopted standards to assure that low-leakage components are used in air conditioning systems designed for heavy-duty pickup trucks and vans, and semi-trucks. The standard for larger A/C systems (capacity above 733 g) is measured in percent total refrigerant leakage per year, while the standard for smaller A/C systems (capacity of 733 g or less) is measured in grams of refrigerant leakage per year.

Costs and benefits

NHSTA and EPA estimate total benefits from the rule of over 1,000 million metric tons of avoided GHG and nearly 2 billion barrels of oil saved over the lifetime of the vehicles sold from 2014–2018. The rule builds on a congressionally mandated study by the National Academy of Sciences (NAS) and previous work by the ICCT and many other stakeholders.

Projected costs, benefits, and vehicle payback periods are listed in the table below. Payback periods are longer for Phase 2 than Phase 1 standards but are still well within the average ownership cycle of the first vehicle owner.