Heavy-duty trucks are the fastest growing contributors to greenhouse gas (GHG) emissions within the
transportation sector, producing nearly 20 percent of GHG and accounting for 17 percent of transportation oil consumption. Because of this, the U.S. Energy Independence and Security Act (EISA) of 2007 directed the National Highway Traffic Safety Administration (NHTSA), in consultation with the Department of Energy (DOE) and the Environmental Protection Agency (EPA), to study the fuel efficiency of heavy-duty trucks and to implement, for the first time ever, fuel-efficiency standards for these vehicles.
 
On September 15, 2011, following a Notice of Proposed Rule Making issued in November 2010, the EPA and NHTSA issued final “Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles” that will begin with model year 2014. The new standards, which will be phased in, apply to model years 2014-2018 and are tailored to each of three main regulatory categories of vehicles:
 

  • Combination tractors, commonly known as semi-trucks that typically pull trailers (Class 7 and 8), although the agencies are not regulating trailers;
  • Vocational vehicles, which comprise a very wide variety of truck and bus types (Class 2b through 8); and
  • Heavy-duty pickup trucks and vans (Class 2b and 3).

 
Incentives are provided to encourage the introduction of advanced technologies, including hybrid powertrains in appropriate applications. In addition to controlling CO2 as a greenhouse gas emission, the EPA rules also cover hydrofluorocarbon standards to control leakage from air conditioning systems in combination tractors, pickup trucks and vans, and nitrous oxide (N2O) and methane (CH4) emissions standards that apply to all heavy-duty engines.
 
The standards for vocational vehicles and combination tractors have separate fuel-consumption standards for vehicles and for engines. Fuel-consumption standards for tractors are expressed in gallons per 1,000 ton-miles (based on tons of freight hauled) and in gallons per 100 bhp-hr for engines. By model year 2018, these standards will require up to a 23 percent reduction in fuel consumption and CO2 emissions relative to the 2010 baseline.
 
The standards for vocational trucks (Class 2b through 8) are also expressed in gallons per 1,000 ton-miles and are set separately for light heavy-duty (Class 2b through 5), medium heavy-duty (Class 6-7), and heavy heavy-duty (Class 8) trucks. Achieving standards for vocational vehicles is limited to engine improvements and tire technologies for reduced rolling resistance. By model year 2018, the standards for vocational vehicles will require up to a 10 percent reduction in fuel consumption and CO2 emissions compared to the 2010 baseline.
 
The standards for heavy-duty pickups and vans (Class 2b and 3) are expressed in gallons per 100 miles with separate standards for gasoline-fueled and diesel-fueled vehicles. The EPA and NHTSA expect industry to apply similar technologies as the 2012-2016 light-duty vehicle CAFE program, but adapted to heavy-duty applications. The standards are fleet-wide corporate average standards as in the case for light-duty vehicles. By model year 2018, the standards will require an average per-vehicle reduction in fuel consumption and CO2 emissions of up to 15 percent for diesel and 10 percent for gasoline vehicles compared to a common 2010 baseline.
 
Over the lifetime of heavy-duty vehicles built for model years 2014-2018, these standards, if successfully met, will promote improvements to overall efficiency that are expected to result in a savings of 530 million barrels of oil and a reduction of 270 million tons of carbon emissions. Achieving these reductions will improve national energy security, reduce air pollution and benefit consumers and businesses with lower costs for transporting goods while spurring innovation in the clean energy technology sector.

Emissions Engine Design Fuel Efficiency Standards

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