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Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.

Fuel EfficiencyFuel Efficiency

Road Rail Air Water

On August 9, 2011, the first set of fuel efficiency standards for heavy duty vehicles was announced by EPA. This page contains a summary of those regulations, plus additional information on factors affecting fuel efficiency for road transportation.


Who is covered by the regulations?

The standards apply directly to engine, vehicle, and equipment manufacturers. Although the standards do not explicitly cover owners and operators of vehicles, they will affect them indirectly, since equipment purchased now will be in service during years when fuel costs and environmental regulations are likely to change significantly.

What is the purpose of the regulations?

Transportation consumes about 2/3 of the oil used in the U.S. every year, much of which is imported. In addition to saving money, improvements in fuel efficiency help reduce this dependence.

In addition to regulatory programs, EPA provides voluntary programs, such as SmartWay, to help industry make the most effective use of available technology and financing to improve fuel efficiency and reduce fuel costs.

Regulations

New federal fuel efficiency and greenhouse gas emission standards for passenger cars and light trucks were established in 2010, applying to the 2012-2016 model years, replacing fuel efficiency standards for passenger vehicles that had been established decades earlier. In 2011, for the first time, new standards for fuel consumption and greenhouse gas emission were established for three classes of heavy duty vehicles:

  • Combination tractors ("semis")
  • Heavy-duty pickup trucks and vans
  • "Vocational vehicles", special purpose vehicles that include, among others:
    • delivery vehicles
    • refuse trucks
    • utility trucks
    • dump trucks
    • cement trucks
    • transit buses
    • shuttle buses
    • school buses
    • emergency vehicles
    • motor homes
    • tow trucks

The standards applying to each of these classes are summarized below. Note that the standards are expressed in terms of fuel consumption rather than fuel economy (as in "gallons per mile" instead of the more familiar "miles per gallon"). Different units are used for different classes of vehicles. Heavy-duty pickups and vans must meet gallon per mile standards (the same combination of units as for passenger vehicles, although expressed upside-down). The other classes, combination tractors and vocational vehicles, must meet gallon per ton-mile standards. This combination of units gives credit for pulling more weight, as well as for traveling a greater distance, on a given amount of gas (since you divide by a larger number in either case). To avoid having to deal with small fractions, the numbers are expressed in slightly modified units, gallons per ton per thousand miles, which multiplies the gallon per ton-mile values by 1,000.

The new standards are somewhat different from previous federal standards applying to trucks. The older standards regulate emissions of pollutants such as nitrogen oxides and smoke particles. It is primarily the engine that determines the level of these pollutants - the rest of the vehicle has comparatively little effect. Those standards accordingly applied most directly to engine manufacturers.

The quantities regulated by the new standards, fuel consumption and greenhouse gas emission levels, also depend on the engine, but in addition they are strongly influenced by the properties of the rest of the vehicle, such as the aerodynamic resistance of the tractor-trailer combination, and the rolling resistance of the tires. For this reason, the new rules apply to manufacturers of vehicles (including those who purchase their engines from other companies) as well as engine manufacturers. Trailers are not covered under the new standards, but will probably be included in future standards.

1. Combination tractors

The standards apply to Class 7 and 8 combination tractors, vehicles whose gross vehicle weight rating, or GVWR (their fully loaded weight), exceeds 26,000 pounds. Trucks within this category are further classified according to their roof height, and whether or not they are sleeper cabs. Different standards apply in each case (see box).

The standards are phased in between 2014 and 2017, and manufacturers have some latitude in how to meet the interim standards. But by 2017, vehicles must meet the standards for fuel consumption and greenhouse gas emissions in the following table:

2017 standards for combination tractors

2017 Model Year
(Gallons of Fuel per 1,000 Ton-Mile)

2017 Model Year GHG emissions (Grams CO2 per Ton-Mile)


Low Roof

Mid Roof

High Roof

Low Roof

Mid Roof

High Roof

Day Cab, Class 7

10.2

11.3

11.8

104

115

120

Day Cab, Class 8

7.8

8.4

8.7

80

86

89

Sleeper Cab, Class 8

6.5

7.2

7.1

66

73

72


Trucks designed for pulling flatbeds are generally designed with a low roof, while trucks designed for pulling box trailers are designed with higher roofs, to match the profiles of the load for better aerodynamics. In general, the standard is less stringent (poorer allowed fuel economy, and higher allowed emissions per mile per ton) for heavier trucks with high roofs, and for trucks with sleeper cabs, as compared to lighter and lower trucks. One reason is to remove any incentive for manufacturers to pass the standard with low-roof cabs that are then used to pull tall box trailers, a lose-lose situation for both operators and fuel economy. Ironically, setting a lower standard removes the incentive to game the system, but unfortunately results in about the same level of emissions that gaming the system would have produced.

Separate standards are being developed that apply specifically to the engines used in Class 7 and 8 vehicles. Engine manufacturers will have to meet the fuel consumption and carbon emissions standards without exceeding limits for other pollutants, such as nitrogen oxides and methane (another greenhouse gas). EPA expects that engine manufacturers will be able to meet the new emissions standards with existing technology.

EPA is developing another separate standard to cover leakage from air conditioning units. Since the refrigerants used in air conditioners are powerful greenhouse gases, a relatively small amount of leakage contributes a disproportionately large share to the vehicle's greenhouse gas emission footprint.

2. Heavy duty pickup trucks and vans

Standards for Class 2b and 3 vehicles (with fully loaded weight between 8500 and 14,000 pounds) are similar to those used for passenger vehicles, with a few exceptions that take into account the way the vehicles are used. The vehicles are tested under load in a standard driving cycle, as with passenger vehicles, but a "work factor" is applied that takes into account the vehicle's payload and its towing capacity. Four-wheel drive vehicles are also allowed somewhat more leeway. The new standards are expected to save 15% in fuel consumption for diesel, and 10% for gasoline powered vehicles. The standards will be phased in between 2014 and 2018.

3. Vocational vehicles

This category covers a wide variety of vehicle types, in weight classes spanning 2b through 8. They tend to be operated at lower speeds, so that improvements in aerodynamic resistance are generally less effective than improvements in rolling resistance. The standards, which will be fully effective in 2017, are directed toward encouraging improvements in engine efficiency and toward the use of tires with less rolling resistance. (Low rolling resistance tires, becoming more common for combination tractors, are still relatively rare for vocational vehicles.)

2017 standards for vocational vehicles

NHTSA Fuel Consumption Standards (gal/1,000 ton-mile)

EPA Full Useful Life Emissions Standards (g CO2/ton-mile)

Light Heavy, Classes 2b-5

36.7

373

Medium Heavy, Classes 6-7

22.1

225

Heavy Heavy, Class 8

21.8

222

Compliance Options

Compliance with the proposed heavy duty truck regulations will be largely the responsibility of vehicle and equipment manufacturers.

However, heavy duty vehicles typically remain in service for decades. Regulations which are unanticipated now might well be enacted during the service life of vehicles being purchased today that could impose requirements on vehicle operators as well as manufacturers. Such regulations could eventually include inspection requirements, or restrictions on vehicle operations. The details are impossible to predict, but as a general rule, whatever regulations are finally put in place will penalize less fuel efficient vehicles at the expense of more efficient ones. Put another way, the relative advantage of a more fuel efficient vehicle will become even more advantageous as rules are phased in. The net effect will be to shorten the payback time for investments in more fuel-efficient technology.

Aerodynamics becomes more and more important as speed increases. A ten percent increase in speed results in an over twenty percent increase in drag (and a correspondingly oversized loss in fuel economy). That's because nature charges two different penalties for speed - the vehicle has to push harder on the air to move through it faster, and the vehicle has to push more air out of the way at a time. The second factor is more significant than it might appear. A typical combination tractor traveling at 60 MPH has to push aside over 16 tons of air every minute.

Adding equipment to improve aerodynamics, such as fairings and wheel well covers, involves a tradeoff between extra fuel costs from the extra weight of the equipment and the fuel savings from reduced drag. Both costs and savings increase as speed increases, but the savings increase faster than the costs. (Extra vehicle weight results in more friction, which increases in proportion to speed. But extra aerodynamic drag, because of the double penalty, increases in proportion to speed squared.) So trucks that spend a lot of time at highway speeds are most likely to see significant reductions in fuel costs - and lower GHG emissions - from aerodynamic retrofits.

Best Practices

Best Practices for Improving Fuel Efficiency (Road Transportation)

The proposed regulations are primarily directed toward manufacturers rather than operators, and are intended to improve the performance of future vehicles. But operators can also take steps to improve fuel efficiency and reduce GHG emissions from existing vehicles.

Two of the most effective ways are to:

In addition to equipment upgrades, operators can realize fuel economy and greenhouse gas emission reduction through operating practices. The EPA SmartWay program provides estimates of the cost savings and emissions reductions that can be realized through measures including:

  • Reducing idling time
  • Optimizing logistics
  • Moderating speed
  • Keeping tires inflated
  • Training drivers in fuel saving driving techniques

EPA Resources

Final rule (Final Text)

The EPA provides an information page on devices and additives that claim to improve fuel economy

 

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