US: Heavy-duty: Fuel Consumption and GHG


Phase 1 standards apply to model years 2014–2018 on-road vehicles with a rated gross vehicle weight of at least 8,500 lbs. Required CO2 and fuel consumption reductions vary by vehicle type and range from 6–23% compared to a model year 2010 baseline. Phase 2 standards cover 2018–2027 and will reduce CO2 and fuel consumption 16% for heavy-duty pickup trucks and vans, 16%–19% for vocational vehicles, and up to 30% for tractor-trailers.

Standard type
Joint fuel consumption standards and GHG emission limits
Regulating Body
US Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA)
All on-road vehicles rated at a GVW≥8,500 lbs


The first joint GHG emissions and fuel consumption standards for heavy- and medium-duty vehicles were adopted in the US in September 2011. In 2010, President Obama requested that the National Highway Traffic Safety Administration (NHTSA) and the US Environmental Protection Agency (EPA) work to jointly establish greenhouse gas (GHG) emissions and fuel efficiency standards for medium- and heavy-duty highway vehicles. This is the first time that either heavy-duty GHG emissions or fuel efficiency have been regulated in the United States. The regulation covers model years (MY) 2014-2018 and applies to all on-road vehicles rated at a GVW≥8,500 lbs.

The rule has several important elements:

  1. Drives efficiency improvements in many important aspects of the heavy-duty vehicle for the two highest fuel consumption classes: tractor trucks and pickup trucks
  2. Sets separate standards for engines and vehicles
  3. Establishes standards for four major greenhouse gases in addition to fuel consumption limits

EPA developed GHG emissions standards under the authority of the Clean Air Act, while NHTSA developed fuel efficiency standards under the 2007 Energy Independence and Security Act (EISA). The emissions included in EPA’s program are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and hydrofluorocarbons (HFCs). The EPA program will begin with MY 2014, while the NHTSA program will be voluntary with MYs 2014 and 2015 and will become mandatory starting with MY 2016. The reason for the difference in timelines is under EISA, NHTSA is required to have four full years of lead-time following the finalization of the rule; EPA has no such lead-time provision under the Clean Air Act.

Overall, the stringency of the program ranges from 6% to 23% reduction in fuel consumption in the MY 2017 timeframe, as compared to a MY 2010 baseline. The stringency levels vary according to vehicle subcategories that are based on weight classes and vehicle attributes. The rule is best understood as three separate regulatory programs linked to specific provisions for tractor trucks, pickup trucks and vans, and vocational vehicles. In addition, the engines that power tractor trucks and vocational vehicles are regulated in a stand-only program.

Technical Standards

Applicability and Exceptions

The affected heavy- and medium-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 MY 2012-2016 light-duty vehicles. CO2 and fuel consumption standards are applicable to three categories of vehicles:

  • Combination tractors (semi trucks that typically pull trailers) – Adopted engine and vehicle standards begin in MY 2014 and achieve 7 to 20% reduction in CO2 emissions and fuel consumption by MY 2017 over the 2010 baselines. While tractors are a key component of this regulation, trailers are not included in the program.
  • Heavy-duty pickup trucks and vans – Standards phase-in beginning MY 2014 and achieve up to a 10% reduction in CO2 emissions and fuel consumption for gasoline vehicles and 15% reduction for diesel vehicles by MY 2018.
  • Vocational vehicles – Engine and vehicle standards start MY 2014 and achieve up to a 10% reduction in fuel consumption and CO2emissions by MY 2017.

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

Fuel economy standards are voluntary in MYs 2014-2015 to satisfy EISA lead time requirements.

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. The standards would phase in to the 2017 levels shown below.

Final (MY 2017) Combination Tractor Standards
Category EPA CO2 Emissions NHTSA Fuel Consumption
g/ton-mile gal/1,000 ton-mile
Low Roof Mid Roof High Roof Low Roof Mid Roof High Roof
Day Cab Class 7 104 115 120 10.2 11.3 11.8
Day Cab Class 8 80 86 89 7.8 8.4 8.7
Sleeper Cab Class 8 66 73 72 6.5 7.2 7.1

The regulation also defines two sets of standards for tractors during the phase-in period: (1) MY 2014 CO2 standards and (2) MY 2014-2016 fuel consumption standards. Manufacturers may voluntarily opt-in to the NHTSA fuel consumption program in 2014 or 2015. Once a manufacturer opts into the NHTSA program it must maintain participation in the program for all the optional MYs.

In addition to vehicle standards, engine-based standards must be met by heavy-heavy-duty (HHD) and medium-heavy-duty (MHD) diesel engines used in combination tractors. As with the vehicle standards, the NHTSA MY 2014 fuel consumption standards for engines are voluntary.

Engine Standards for Engines Installed in Tractors
Category Year CO2 Emissions Fuel Consumption
g/bhp-hr gallon/100 bhp-hr
MHD Engines 2014 502 4.93
2017 487 4.78
HHD Engines 2014 475 4.67
2017 460 4.52

An optional compliance schedule is available, with more relaxed tractor engine standards to be met from 2013 and numerically identical final standards to be met from 2016.

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 a set of target standard curves, based on a “work factor” that combines a vehicle’s payload, towing capabilities, and whether or not it has 4-wheel drive. The standards will phase in with increasing stringency in each model year from 2014 to 2018. 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 (though not including the EPA’s air conditioning leakage standard).

Both agencies are providing manufacturers with two alternative phase-in approaches. One alternative 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 model years 2014-2015-2016-2017-2018-2019.

Vocational Trucks

This vehicle segment has been divided into three regulatory subcategories—Light Heavy (Class 2b through 5), Medium Heavy (Class 6 and 7), and Heavy Heavy (Class 8)—which is consistent with engine classifications. The respective vehicle standards are depicted below.

Final (MY 2017) Vocational Vehicle Standards
Category EPA CO2 Emissions NHTSA Fuel Consumption
g/ton-mile gal/1,000 ton-mile
Light Heavy Class 2b-5 373 36.7
Medium Heavy Class 6-7 225 22.1
Heavy Heavy Class 8 222 21.8

Engine standards for light heavy-duty (LHD), medium heavy-duty (MHD), heavy heavy-duty (HHD) diesel engines and for heavy-duty gasoline engines are shown below. MY 2014-2016 diesel fuel consumption standards are voluntary.

Engine Standards for Engines Installed in Vocational Vehicles
Category Year CO2 Emissions Fuel Consumption
g/bhp-hr gallon/100 bhp-hr
LHD Engines 2014 600 5.89
2017 576 5.66
MHD Engines 2014 600 5.89
2017 576 5.66
HHD Engines 2014 567 5.57
2017 555 5.45
Gasoline Engines 2016 627 7.06

An optional compliance schedule is available for vocational engines, structured in a similar way to that for tractor engines.


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.

Chassis manufacturers are subject to the vehicle standards. Vehicle standards compliance is determined based on a vehicle simulation model, called the Greenhouse gas Emission Model (GEM), developed by EPA specifically for this regulation. 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 the model. These characteristics relate to key technologies applicable to a given truck category—for tractors, this includes aerodynamic features, weight reductions, tire rolling resistance, the presence of idle-reducing technology, and vehicle speed limiters. For vocational vehicles, the only inputs into the GEM are the tire rolling resistance values, which are determined using a laboratory drum test.

Useful Life

EPA CO2 emissions must be met over the engine’s and vehicle’s useful life. The useful life definitions for engines and for vehicles that use the respective engine categories are identical to those defined for criteria pollutant standards for MY 2004 and later heavy-duty engines:

  • LHDDE—110,000 miles/10 years
  • MHDDE—185,000 miles/10 years
  • HHDDE—435,000 miles/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, consistent with N2O/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, which will affect vehicles beginning with model year 2014, of nearly 250 million metric tons of avoided GHGs and approximately 500 million barrels of oil saved over the lifetime of the vehicles sold during 2014 to 2018. Using estimates for climate, energy security, and air pollution externalities, the agencies estimate total societal benefits of $49 billion, which is a net benefit of $41 billion after accounting for the estimated $7.7 billion in costs to industry. 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 per-vehicle costs and fuel savings are summarized in the table below. For tractor trucks, given the high number of annual miles these vehicles typically travel, the payback period per vehicle will generally be less than a year. For heavy-duty pickup trucks and vans the period will be slightly longer, as these vehicles average much less annual mileage so the fuel savings take longer to accrue. For vocational vehicles, the estimated fuel savings of roughly $700 in year one is larger than the modest cost increase of $378, thus making the payback time less than a year.

Estimated Cost-Benefit, MY 2018 Vehicles (2009 dollars)
Vehicle category Cost per truck Lifetime fuel savings Reference in the regulation
Tractor trucks $6,215 $79,089 Table VIII-11
HD pickups and vans $1,048 $7,187 Table VIII-9
Vocational vehicles $378 $5,872 Table VIII-10

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