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NHTSA, EPA propose first greenhouse gas and fuel efficiency standards for heavy-duty trucks and buses

The US Environmental Protection Agency (EPA) and the US Department of Transportation’s (DOT) National Highway Traffic Safety Administration (NHTSA) have announced a proposed rulemaking for the first national standards to reduce greenhouse gas (GHG) emissions and improve fuel efficiency of heavy-duty trucks and buses. These vehicles make up the transportation segment’s second-largest contributor to oil consumption and GHG emissions.

The agencies are each proposing complementary standards under their respective authorities covering model years 2014-2018, which together would form a comprehensive HD National Program. EPA and NHTSA are proposing emission standards for CO2 and fuel consumption standards, respectively, tailored to each of three main regulatory categories: combination tractors; heavy-duty pickup trucks and vans; and vocational vehicles (including buses and refuse or utility trucks). EPA is additionally proposing standards for air conditioning related emissions of HFC from pickups, vans and tractors; as well as N2O and CH4 standards applicable to all heavy-duty engines, pickups and vans.

For purposes of the proposed rulemaking, the heavy-duty fleet incorporates all on-road vehicles rated at a gross vehicle weight at or above 8,500 pounds, and the engines that power them, except those covered by the current GHG emissions and Corporate Average Fuel Economy standards for model years 2012-2016.

The agencies’ scopes are the same except that EPA is proposing to include recreational on-highway vehicles (RV’s, or motor homes) within its rulemaking, while NHTSA is not including these vehicles, due to EISA’s requirement that standards be set for “commercial” medium- and heavy-duty on-highway vehicles and work trucks.

The joint proposed standards cover not only engines but also the complete vehicle, allowing the agencies to achieve the greatest possible reductions in fuel consumption and GHG emissions, while avoiding unintended consequences. New technologies envisioned to meet the new regulations include widespread use of aerodynamic improvements and tire rolling resistance, as well as engine and transmission upgrades.

Proposed metrics. The majority of these vehicles carry payloads of goods or equipment, in addition to passengers. To account for this in the regulatory program, two types of standard metrics are proposed:

  • Payload-dependent gram per mile (and gallon per 100-mile) standards for pickups and vans; and
  • Gram per ton-mile (and gallon per 1,000 ton-mile) standards proposed for vocational vehicles and combination tractors.

The agencies said that these proposed metrics account for the fact that the work to move heavier loads burns more fuel, and emits more CO2 than in moving lighter loads.

Combination tractors. The agencies are proposing differentiated standards 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 in the table below. These proposed standards would achieve from 7-20% reduction in emissions and fuel consumption from affected tractors over the 2010 baselines.

Proposed MY 2017 Combination Tractor Standards
  EPA Emissions Standards
(g CO2/ton-mile)
NHTSA Fuel Consumption Standards
(gal/1,000 ton-mile)
Low RoofMid RoofHigh RoofLow RoofMid RoofHigh Roof
Day Cab Class 7 103 103 116 10.1 10.1 11.4
Day Cab Class 8 78 78 86 7.7 7.7 8.5
Sleeper Cab Class 8 64 69 71 6.3 6.8 7.0

Heavy-Duty Pickup Trucks and Vans. The agencies are proposing to set corporate average standards for heavy-duty pickup trucks and vans, similar to the approach taken for light-duty vehicles. Each manufacturer’s standard for a model year would depend on its sales mix, with higher capacity vehicles (payload and towing) having numerically less stringent target levels, and with an added adjustment for 4-wheel drive vehicles. This approach recognizes both the inherently higher GHG emissions and fuel consumption of higher-capacity vehicles, and the importance of payload and towing capacity to the owners of these work trucks and vans.

EPA is proposing to establish standards for this segment 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 would phase in with increasing stringency in each model year from 2014 to 2018. The EPA standards proposed for 2018 (including a separate standard to control air conditioning system leakage) represent an average per-vehicle reduction in GHG emissions of 17% for diesel vehicles and 12% for gasoline vehicles, compared to a common baseline.

NHTSA is proposing to set corporate average standards for fuel consumption that are equivalent to EPA’s proposal, but without the air conditioning leakage standard. (though not including EPA’s proposed air conditioning leakage standard). The proposed NHTSA standards represent an average per-vehicle improvement in fuel consumption of 15% for diesel vehicles and 10% for gasoline vehicles, compared to a common baseline.

To satisfy lead time requirements under EISA, NHTSA standards would be voluntary in 2014 and 2015. Both agencies are proposing to provide manufacturers with two alternative phase-in approaches that get equivalent overall reductions. 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. In these rules, the agencies are proposing to regulate chassis manufacturers for this segment. The agencies are proposing to divide this segment 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 the engine classification.

After engines, tires are the second largest contributor to energy losses of vocational vehicles. The proposed program for vocational vehicles for this phase of regulatory standards is limited to tire technologies and hybrid powertrains (along with the separate engine standards). The proposed standards depicted in the table below represent emission reductions from 7 to 10%, from a 2010 baseline.

Proposed MY 2017 Vocational Vehicle Standards
  EPA Emissions Standards
(g CO2/ton-mile)
NHTSA Fuel Consumption Standards
(gal/1,000 ton-mile)
Light Heavy Class 3-5 344 33.8
Medium Heavy Class 6-7 204 20
Heavy Heavy Class 8 107 10.5

N2O, CH4 and HFC Standards. EPA’s proposed standards would act to cap emissions to ensure that manufacturers do not allow the N2O and CH4 emissions of their future engines to increase significantly above the currently controlled low levels.

Air conditioning systems contribute to GHG emissions in two ways: direct emissions through refrigerant leakage and indirect emissions due to the extra load on the vehicle’s engine to provide power to the air conditioning system. HFC refrigerants, which are powerful GHG pollutants, can leak from the A/C system. EPA is proposing a standard of 1.5% refrigerant leakage per year, to assure that high-quality, low-leakage components are used in each air conditioning system design for pickup trucks, vans, and tractors.

Flexibilities. The HD National Program would provide flexibilities to manufacturers in terms of how they could comply with the new standards. The primary proposed flexibility provisions are an engine averaging, banking, and trading (ABT) program and a vehicle ABT (averaged, banked or traded) program. These ABT programs would function within each of the regulatory subcategories; credits would not be allowed to be transferred across categories.

In addition to the general ABT programs, EPA is proposing to allow engine manufacturers the added option of using CO2 credits to offset CH4 or N2O emissions that exceed the applicable emission standards based on the relative global warming potentials of these emissions.

The structure of the proposed ABT program for HD engines is based closely on earlier EPA ABT programs for HD engines; the proposed program for pickup trucks and vans is built on the existing light-duty fuel economy credit carry-forward, carry-back, trading and transferring provisions; and first-time ABT provisions are proposed for HD vehicle manufacturers that are as consistent as possible with the provisions for other categories.

The agencies are proposing three additional optional credit opportunities:

  • An early credit option intended for manufacturers who demonstrate improvements in excess of a proposed standard prior to the model year that it becomes effective.
  • A credit program intended to promote implementation of advanced technologies, such as hybrid powertrains, Rankine cycle engines, and electric or fuel cell vehicles.
  • A credit intended to apply to new and innovative technologies that reduce vehicle CO2 emissions and fuel consumption, but for which the benefits are not captured over the test procedure used to determine compliance with the standards (i.e., “off-cycle”).

Anticipated benefits. The agencies project that the national program will reduce GHG emissions by about 250 million metric tons and save 500 million barrels of oil over the lives of the vehicles produced within the program’s first five years.

Overall, NHTSA and EPA estimate that the heavy-duty national program would provide $41 billion in net benefits over the lifetime of model year 2014 to 2018 vehicles. With the potential for significant fuel efficiency gains, ranging from 7 to 20%, drivers and operators could expect to net significant savings over the long-term.

For example, they estimate an operator of a semi truck could pay for the technology upgrades in under a year, and save as much as $74,000 over the truck’s useful life. Vehicles with lower annual miles would typically experience longer payback periods, up to four or five years, but would still reap cost-savings.

EPA and NHTSA are providing a 60-day comment period that begins when the proposal is published in the Federal Register.

As part of the process of developing this proposed rulemaking, NHTSA has prepared a draft Environmental Impact Statement (EIS) for its proposed fuel efficiency standards. The draft EIS compares the environmental impacts of the agency’s proposal with those of a number of regulatory alternatives. Comments may be submitted on the Draft EIS through 3 January 2011.




The direct relationship between GHG and fuel consumption seems to be maintained. Wouldn't future cleaner fuels and more efficient fuel burning engines change that relationship? Would hydrogen injection help?

Many of those heavy trucks are great polluters, as much as 30 mid-size cars and more. They should be called upon to fix their act.

Henry Gibson

Trucks move a lot more pounds and rail shipment is a lot more efficient, the bigger problem is the cost of repairing their damage to the roads. In regards to CO2 release per ton-mile delivered they are far more efficient than automobiles. A small diesel engine generator with flywheel energy storage could easily outperform the batteries in a TESLA with much lower weight. Remember OPOC. ..HG..


These agencies keep doing the same old thing expecting different results - i.e. insanity. And wasting taxpayer funds.

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