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Heavy-Duty Vehicles Module

This Stochastic Energy Deployment System (SEDS) module covers heavy-duty vehicles (HDVs) and off-road transportation for the United States. The module estimates energy consumption by fuel type for six subsectors:

  • Heavy highway vehicles
  • Aviation
  • Railroads
  • Pipelines
  • Water transport
  • Other off-highway modes.

Energy demand estimation procedures were developed after evaluating various attributes of each subsector. Macroeconomic, commodity demand, and fuel price information from other modules are used in estimating energy demand. Vehicle survival and age-dependent usage models track medium and heavy trucks from the year of purchase until they are scrapped.

Focus of Analysis

The module analyzes the effects of petroleum prices, commodity-dependent freight mode energy demand, exogenously evaluated changes in HDV and aircraft fuel economy, and macroeconomic changes. The module generates fuel consumption and carbon dioxide emissions estimates for each scenario simulated.

Limitations of Analyses

The module cannot simulate regional differences and variations in subsector energy intensity in the different parts of the United States. Other items that cannot be simulated explicitly include behavioral differences relating to modal preferences and effects of temporary price incentives. A drawback in the water freight section includes the lack of international accounting. It would be difficult to set new standards for international vessels because most of them are registered in foreign countries.

Technologies of Interest to U.S. Department of Energy

The module assumes the HDV sector to continue to rely on petroleum-based fuels and natural gas. Increased share of new diesel-powered trucks can be evaluated. Aviation sector fuel economy improvements for domestic and international travel can be simulated separately. Impacts of increased demand for coal on railroad and water mode energy demand can be simulated.

Overview of Methodology


The truck subsector of the HDV module categorizes trucks into medium-duty and heavy-duty trucks. Historical truck sales for the period 1975-2005 are included in the module database, while projected sales are estimated based on gross domestic product (GDP) and population.

Vehicle survival and age-dependent usage functions are applied and estimates of vehicles on road (vehicle stock) and vehicle miles of travel (VMT) are developed for each vintage. Exponential vehicle survival functions are based on truck survival data from Oak Ridge National Laboratory's Transportation Energy Data Book.

Truck usages in terms of annual miles per truck were compiled from Census Bureau's Vehicle Inventory and Use Surveys. Cubic functions for age-dependent annual miles per truck are applied to estimate VMT for each vintage and truck type. VMT elasticity based on fuel price is also included in this subsector, with the default value set to -0.1 (meaning a 10% increase in fuel cost per mile decreases VMT by 1%) for both medium and heavy trucks.

Truck fuel economy for each vintage is carried forward and fuel consumption by each truck vintage is estimated. The sum of fuel consumption by all vintages provides annual fuel consumption for each truck type. Truck energy demand is allocated among gasoline, diesel, compressed natural gas (CNG), and liquefied petroleum gas (LPG) fuels. The vast majority of truck fuel is diesel. Gasoline share is expected to decrease to 3%, CNG to grow to 0.7%, and LPG to go to zero by 2050.


Bus energy demand is computed as a function of GDP and crude cost. The dominant bus fuel is diesel. Other fuels in use as of 2005 are gasoline, CNG, and electricity. The use of both gasoline and electricity has been declining and is expected to be zero by 2020. The use of CNG has increased due to stricter bus emissions regulations. However, the better performing diesel hybrid electric buses are assumed to replace CNG buses over time.


The aviation sector is divided into domestic commercial aviation, international commercial aviation, and general aviation. Domestic and international commercial aviation travel demands (revenue passenger miles) are estimated as functions of GDP, population, and crude price. These two segments have different energy intensities and their historical rates of improvements in fuel intensities are also different. The commercial aviation energy intensities for domestic and international travel will continue to improve with the rates of improvement declining over time. General aviation energy demand is directly estimated as a function of per capita income.


The rail mode uses diesel and electricity. Most of the energy use is as diesel fuel while electricity use is by urban rail transit plus some by electrified rail lines in the northeast. Coal, chemicals and allied products, farm products, nonmetallic minerals, and food and kindred products are the five major commodities moved by railroads with coal accounting for over 40% of tonnage and nearly half of ton-miles. Freight rail energy intensity is estimated as gallons of diesel per ton-mile. Ton-miles are estimated as a function of coal demand. Diesel demand is calculated by combing energy intensity with ton-miles traveled. Railroad electricity use is kept constant at the 2005 level.


Pipelines use natural gas and electricity. Pipeline natural gas use is estimated as a function of total natural gas demand and electricity use is estimated as a function of petroleum products and crude oil demands.

Water Transport

The water mode uses gasoline, diesel, and residual fuel oil. The gasoline use is for recreation activities and is trended within the module. Water mode's diesel and residual fuel demand is estimated as a function of crude oil cost, U.S. coal demand, and U.S. distillate fuel oil demand. The water mode also includes fuel price elasticities, which decrease fuel use with increasing fuel price. The default value of recreational water elasticity is set to -0.1, while freight water elasticity is -0.15. The rate of growth in diesel fuel is projected as a function of time and the resulting diesel use is estimated. The remainder is estimated as residual fuel oil use.

Off-Highway Vehicles

The other off-highway modes include farm equipment and construction and earth-moving machines. The fuels consumed are gasoline and diesel. The total energy use is estimated as a function of gross domestic product and crude cost. The use of gasoline is trended and subtracted from the total to arrive at diesel use.

Carbon dioxide emissions are estimated as carbon contents of a fuel minus carbon not converted to carbon dioxide times the carbon dioxide conversion factor. The amount of carbon not converted to carbon dioxide is assumed to be 1%.

Major Assumptions

The heavy-duty subsectors are heavily dependent on economic changes and crude price. Some fuel consumption values are trended assuming GDP will continue to grow by more than 1% per year.

Stochastic Inputs

Stochastic inputs include medium and heavy truck fuel economy, and commercial aviation and freight rail energy intensities.

Key Inputs from Other Modules

  1. Crude oil price
  2. Diesel price
  3. GDP
  4. Population
  5. Total demand for crude oil, coal, natural gas, and petroleum products

Key Outputs to Other Modules

  1. Heavy duty demand for gasoline, diesel, jet fuel, natural gas, electricity, and residual fuel oil
  2. Carbon dioxide emissions


SEDS Transportation Sector Modules


Anant Vyas, Argonne National Laboratory

Deena Patel, Argonne National Laboratory