Transportation Modes Overview
Transportation Modes Overview CLIMATE TECHBOOK Quick Facts •
Transportation activity and vehicle ownership is expected to grow significantly in all countries over the next 50 years. Over the next two decades, passenger vehicle ownership is expected to double worldwide, with most of the increase occurring in non-OECD countries.
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Passenger or light-duty vehicles are the largest source of energy consumption and greenhouse gas (GHG) emissions within the transportation sector. Medium- or heavy-duty vehicles make up many commercial vehicle fleets; these fleets consume large quantities of fuel because of intensive use and the low fuel economy of their vehicles.
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Aircraft emissions in the United States are a small percentage of total transportation sector emissions, but are expected to grow significantly over the long term. Emissions from marine transportation are a very small percentage of current transportation sector emissions in the United States, with little domestic growth expected over the next 30 years.
Background The transportation sector consists of cars and light-duty trucks (also referred to as passenger vehicles), medium- and heavy-duty trucks, buses, trains, ships, and aircraft. Energy use and, as a result, greenhouse gas (GHG) emissions from each mode are determined by four major elements: the fuels used and their carbon content, the efficiency of each vehicle, the distance traveled, and the overall efficiency in transportation system operations (See Climate TechBook: Transportation Overview). Of the various transportation modes, passenger vehicles consume the most energy (see Figure 1). GHG emissions mirror energy use by each mode, because all modes use petroleum fuels with similar carbon contents and thus result in corresponding shares of GHG emissions. Figure 1: Transportation Energy Use by Mode (2007) Pipeline, 3.2%
Rail, 2.3%
Water, 5.6%
Air, 9.0%
Medium/heavy trucks, 18.8%
Light vehicles, 60.4%
Buses, 0.7% Source: Department of Energy (DOE), Transportation Energy Data Book, 2008.
Page | 1 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Over the next 20 years, analysts expect energy use for rail, aircraft, buses, and freight trucks to grow at higher average annual rates compared to energy use in light-duty vehicles (see Figure 2). Figure 2: Average Annual Growth in Transportation Energy Use by Mode (2008-2035) 1.4% 1.2% 1.0% 0.8% 0.6% 0.4% 0.2% 0.0%
Source: Department of Energy (DOE), Annual Energy Outlook Early Release, January 2010.
This factsheet gives a brief overview of the various transportation modes and discusses efficiency improvements available for each.
Passenger Vehicles Passenger or light-duty vehicles are defined as cars or light-trucks with a gross vehicle weight of less than 8,500 pounds. They are the largest source of energy consumption and GHG emissions within the transportation sector. Table 1: Passenger Vehicles in the United States
Cars New Vehicle Sales and Leases (Thousands, 2008) Total Vehicle Registrations (Thousands, 2007) Vehicle Miles Traveled (Millions, 2007) Average Vehicle Occupancy Rate (2006) Average Fuel Economy (2007) Average New Vehicle Fuel Economy (2008) CAFE Standard (2008)
Total
6,806
Light Trucks 6,388
135,933
101,470
237,403
1,670,994 1,111,277 1.58 1.73 22.5 31.2
18.0 23.6
27.5
22.5
13,195
2,782,271
27.0
Page | 2 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Source: Department of Transportation, Bureau of Transportation, National Transportation Statistics, 2009.
Technology options to reduce fuel consumption and GHG emissions from passenger vehicles can include the following: •
The technological improvements for light-duty vehicles can be grouped according to application: engine efficiency, transmission, and other improvements, which include vehicle weight reduction, aerodynamic improvements, and reduced rolling resistance. With full implementation of these technologies for fuel economy gains, oil consumption and GHG emissions per mile could be reduced by more than 40 percent by 2035, and about 50 percent by 2050 compared to average vehicles in 2006. 1
•
Hybrid vehicle technologies can also reduce gasoline consumption and GHG emission. There is a range of hybrid electric vehicles available today, and they are expected to make up about 20 percent of annual vehicle sales by 2015 and nearly 40 percent by 2030. 2
•
Plug-in hybrid electric and all-electric vehicles (PEVs) offer considerable improvements in engine efficiency over conventional hybrid vehicles because an electric motor can power the vehicle, in addition to the engine drivetrain. General Motors plans to deploy the first mass-produced plug-in hybrid electric vehicle, the Chevrolet Volt, in late 2010. Nissan also plans to release the first massmarket all-electric vehicle in late 2010. Key hurdles for PEVs include battery capacity, durability, and cost, as well as the infrastructure needed to charge batteries.
•
Hydrogen fuel cell vehicles produce electricity in fuel cells, which is then used to power the vehicle. Fuel cells promise a two- to three-fold increase in vehicle efficiency over conventional internal combustion engine (ICE) vehicles and emit only water vapor on use. Similar to electric vehicles, storing enough hydrogen to obtain sufficient vehicle range before refueling is a challenge, especially given the current lack of a convenient refueling infrastructure. Hydrogen vehicles can partially compensate for this problem by being significantly more efficient than ICE engines, thus requiring the storage of less on-board energy. Durability and costs of fuel cells and hydrogen production also remain challenges.
•
The passenger vehicle market has been the focus of biofuels use and research thus far. Biofuels used currently include ethanol, biodiesel, and other fuels derived from biomass. To obtain significant reductions in GHG emissions using biofuels in light-duty vehicles, a transition to advanced biofuels with significantly lower GHG emission profiles will be required. (See Climate Techbook: Biofuels Overview).
Medium- and Heavy-Duty Vehicles Vehicles in the medium-duty category have a gross vehicle weight of 8,500 to 26,000 pounds and include everything from large pick-up trucks and SUVs, small buses, cargo vans, and short-haul trucks. Heavy-duty vehicles (HDVs) have a vehicle weight over 26,000 pounds and are used in both long-distance and local transport. HDVs include long-haul trucks, large buses, and other vehicles. Medium- or heavy-duty vehicles
Page | 3 May 2010
Transportation Modes Overview CLIMATE TECHBOOK (e.g., freight and delivery trucks) make up many commercial vehicle fleets; these fleets consume large quantities of fuel because of intensive use and the low fuel economy of their vehicles.
Table 2: Medium- and Heavy-Duty Trucks in the United States, 2002
Number of Registered Vehicles
Medium‐duty trucks Heavy‐duty trucks
2,858,368 2,333,786
Percentage of Overall Truck Registrations 3.40% 2.70%
Average Average Fuel Percentage Annual Miles Economy of Overall per Truck (mpg) Truck Fuel Use 13,237 8.0 5.20% 44,581 5.8 21.60%
Source: Department of Energy (DOE), Transportation Energy Data Energy Book, 2008.
Technology options to reduce fuel consumption and GHG emissions can include the following: •
A significant amount of fuel use could be avoided by reducing vehicle idling – an average tractortrailer spends six hours each day idling to generate electricity for AC and heating systems. 3 Idle reduction technologies can include, e.g., auxiliary power units in vehicles or electrical outlets at truck stops that allow drivers to “plug in” their vehicles to operate the necessary systems. Hybrid drivetrains, similar to those used in passenger vehicles, can also help reduce idling, especially for vehicles used locally in stop and go traffic. Estimates suggest that hybrid systems have the potential to improve fuel economy by 25 to 70 percent in comparison to a standard diesel engine. 4 In the case of buses, idle reduction technologies and strategies have the co-benefit of improving air quality in areas of heavy bus use, such as schools.
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Overall, there is less potential for improving fuel efficiency in these vehicles, compared to passenger vehicles. Most medium- and heavy-duty vehicles have turbo-charged, 5 direct-injection diesel engines, which are the most energy-efficient internal combustion engines available. State-of-the-art turbocharged diesel engines achieve 46 to 47 percent efficiency, versus only 25 percent for spark-ignited gasoline engines, which are used in most passenger vehicles in the United States. Options for improving medium- and heavy-duty vehicle efficiency include engine improvements, transmission enhancements, improved aerodynamics and changes in systems and logistics. If all these measures were fully implemented, the fuel consumption of new trucks could be reduced by 20 percent starting in 2012 and up to 50 percent in 2017. 6
•
These modes can also benefit from alternative fuel use. Lower carbon fossil fuels, such as natural gas, can reduce conventional air pollutants as well as GHG emissions. 7 For diesel-powered trucks, biodiesel blends of up to 20 percent biodiesel can be used in engines without any modification. (See Climate TechBook: Biodiesel.)
•
The U.S. Environmental Protection Agency has two programs – SmartWay Tractors and Trailers and the SmartWay Transport Partnership – which are both designed to help truck owners and freight
Page | 4 May 2010
Transportation Modes Overview CLIMATE TECHBOOK transport operators choose the most efficient vehicles and save energy and lower operating costs through improved logistics. 8
Aircraft Aircraft emissions in the United States are a small percentage of total transportation sector emissions, but are expected to grow significantly over the long term. Business-as-usual (BAU) projections for aircraft energy consumption growth in the United States are estimated at a little less than 1 percent per year over the next 25 years. 9 Table 3: Certificated Air Carrier Statistics for the United States, 2006
Number of Aircraft Aircraft‐miles (millions) Available seat‐miles (millions) Passenger‐miles (millions) Fuel consumed (million gallons) Seats per aircraft Seat‐miles per gallon Energy intensity (Btu/passenger‐mile) Load factor (percent)
Domestic operations 8,225 (2005) 6,511 742,461 591,834 13,458 114.0 55 3,070 79.0
International operations 1,428 266,725 220,138 5,827 186.8 46 3,574 79.9
Source: Department of Transportation, Bureau of Transportation, National Transportation Statistics, 2009.
A number of options are available to limit the growth in aviation GHG emissions. These include improved navigation systems in the near to medium term and advanced propulsion systems, lightweight materials, improved aerodynamics, new airframe designs, and alternative fuels over the medium to long term. •
In the near term (to 2025), the most promising strategies for improving the efficiency of aircraft operations are improvements to the aviation system: advanced communications, navigation and surveillance (CNS) and air traffic management (ATM), as opposed to changes to aircraft themselves. These improvements have the potential to decrease aircraft fuel consumption and improve aviation operations by shortening travel distances and reducing congestion in the air and on the ground.
•
Over the longer term (out to 2050), efficiency improvements can be achieved by aircraft technologies that include more efficient engines, advanced lightweight materials, and improved aerodynamics. Since aircraft have a much longer lifetime than on-road vehicles (30 to 40 years compared to an average of 14 years for a passenger vehicle in the United States), the fleet-wide penetration of advanced technologies will take a number of years. Early aircraft retirement programs might be able to push more rapid fleet turnover, but the potential benefits of such a program are uncertain.
•
The potential for fuel switching on jet aircraft is limited in the short term, compared to on-road vehicles. The only feasible options for “drop-in” replacements to petroleum-based jet fuels include hydroprocessed renewable jet fuel (HRJ) (from plants or algae) and thermochemically produced Fischer-Tropsch (FT) fuels (from biomass or fossil fuel feedstocks, if produced with carbon capture
Page | 5 May 2010
Transportation Modes Overview CLIMATE TECHBOOK and storage). Neither of these fuel production processes is commercial at this stage, and their use over the longer term also faces numerous challenges with respect to their production, distribution, cost, and the magnitude of GHG benefits that can ultimately be achieved by using them.
Marine Transportation Emissions from marine transportation are a very small percentage of current transportation sector emissions in the United States, with little domestic growth expected over the next 30 years. On the other hand, due to increases in economic activity and international trade, international marine emissions are estimated to increase by at least 50 percent over 2007 levels by 2050, under business-as-usual conditions. Table 4: Marine Transportation Statistics
Number of Vessels
Ton‐miles (billions)
Domestic Tons shipped (millions)
41,109
562
1,024
Domestics Tons shipped as percentage of total 39.6
Average length of haul (miles)
Energy intensity (Btu/ton‐ mile)
Energy use (trillion Btu)
548.7
513
288.1
Source: Department of Energy (DOE), Transportation Energy Data Energy Book, 2008.
The majority of marine vessels used for commercial operations are powered by highly efficient diesel engines. 10 These engines generally have a longer lifetime than those used in on-road transportation (30 years or more); thus, technical improvements to new engines might not reduce emissions in the shorter term. •
Immediate reductions in GHG emissions from marine vessels are available by simply reducing speed. However, reducing speed also reduces shipping capacity. To maintain shipping supply, more frequent trips or increasing ship utilization (the load factor) would be required. Although more frequent trips could increase GHG emissions, reductions in shipping supply from reduced speeds can also be countered by increasing port efficiency and optimizing land-side inter-modal transport systems, allowing for faster ship turnaround times.
•
Additional optimization of shipping logistics, routing and maintenance could reduce GHG emissions from shipping. These improvements include increased ship utilization (increased load factor), improved and more consistent maintenance practices, optimized ship control, and route planning optimized for current weather conditions and ocean currents.
•
Technological mitigation options for new ships, aside from alternative fuels and power, include larger ship sizes, hull and propeller optimization, more efficient engines and novel low-resistance hull coatings. Improvements in engine design include a more flexible design utilizing a series of smaller diesel-electric engines, each optimized for a single speed, that power an electric drive.
•
In the marine sector, most alternative energy sources currently in use or under development for application in other sectors could be applied to ships as well. Substituting marine diesel oil or liquefied natural gas for heavy fuel oil (i.e., residual fuel oil) currently used in ships can achieve GHG reductions. Other alternative fuel and power sources, such as biofuels, solar photovoltaic cells, and fuel cells, are longer-term options. Page | 6 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Other Modes Rail transportation and buses are a very small percentage of current transportation sector emissions in the United States, yet growth rates for energy consumption within these modes are expected to be higher than that for other modes, with the exception of freight trucks. The rail transportation system is used for both freight and passenger travel. Passenger travel includes intercity, transit, and commuter rail systems. Buses are also used for transit and intercity travel, as well as for school transportation. In the future, these modes could make use of technological advances in other sectors, such as improvements in diesel engine efficiency, hybrid technologies, and alternative fuels. For example, many metropolitan transit systems are transitioning to natural gas buses. In 2004, about 12 percent of transit buses were powered by natural gas, and since then many transit systems have increased their natural gas bus fleets. 11
Global Context Transportation activity and vehicle ownership is expected to grow significantly in all countries over the next 50 years. Over the next two decades, passenger vehicle ownership is expected to double worldwide, with most of the increase occurring in non-OECD countries. The use of air travel and marine shipping is also expected to increase rapidly, with faster growth rates outside of the United States. Many of the non-OECD economies are predicted to experience rapid growth in energy consumption as transportation systems are modernized and the demand for personal motor vehicle ownership increases due to higher per capita incomes. Under business-as-usual conditions, non-OECD transportation energy use is expected to increase by an average of 2.7 percent per year from 2006 to 2030, compared with an average of 0.3 percent per year for transportation energy consumption in the OECD countries. 12
Policy Options A range of policy options is available for reducing GHG emissions from these various modes of transportation. Policies can include pricing policies, fuel economy or GHG emission standards, and funding for technology R&D. •
Pricing policy options include feebates, taxes on inefficient vehicles, and tax credits for purchase of fuel-efficient vehicles. A feebate can be formulated in terms of fuel economy (fuel consumption per unit distance) or GHG emissions. The manufacturer (or the purchaser) pays a fee for any vehicles produced (or purchased) that are less efficient than the target level for fuel economy or GHG emissions. The purchasers of any vehicle produced or sold that is more efficient than the target receive a rebate. The value of the fee or rebate can increase in proportion to the divergence from the targeted value. The feebate changes the initial purchase price of a vehicle, which can have a larger impact on consumer decisions than the savings from higher fuel economy alone.
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In the United States and worldwide, vehicle standards have been the main mechanism for improving the efficiency of passenger vehicles. Vehicle fuel economy standards can be expressed in miles per gallon (mpg) or kilometers per liter (km/l). Vehicle emissions standards limit GHG emissions from a vehicle and are typically expressed as grams of CO2 equivalent per kilometer (gCO2e/km).
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For other modes of transportation, low sales volumes and varied product configurations and applications make it difficult to set standards. For example, in the United States, annual sales in the heavy-duty sector are less than five percent of the annual light-duty vehicle sales. These modes can benefit from programs that quantify and create incentives for operators to use the most efficient equipment and operations. For example, EPA’s SmartWay Transport Partnership works with freight
Page | 7 May 2010
Transportation Modes Overview CLIMATE TECHBOOK •
truck operators to monitor and reduce fuel consumption, GHG emissions, and air pollutants. Similar efforts can be directed to other modes, such as metropolitan areas with large bus fleets. Policies to address GHG emissions from international aviation and marine shipping are especially challenging, because they are produced along routes where no single nation has regulatory authority. Two broad policy options are available for controlling emissions from international transportation: continuing work under the International Civil Aviation Organization and International Marine Organization to construct an international agreement for addressing these emissions; or assigning responsibility for these emissions to parties for inclusion in national commitments to reducing GHG emission.
Related Business Environmental Leadership Council (BELC) Company Activities • • • • • • •
Boeing Daimler Deere and Company GE Lockheed Martin Toyota United Technologies
Related Pew Center Resources Aviation and Marine Transportation: GHG Mitigation Potential and Challenges, 2009 Policies to Reduce Emissions from the Transportation Sector, 2008 Reducing Greenhouse Gas Emissions from U.S. Transportation, 2003 Federal Vehicle Standards Comparison of Passenger Vehicle Fuel Economy and GHG Emission Standards around the World Map: State Vehicle Greenhouse Gas Emissions Standards
Further Reading / Additional Resources U.S. Department of Energy, Alternative and Advanced Vehicles U.S. Department of Transportation, National Transportation Statistics
Page | 8 May 2010
Transportation Modes Overview CLIMATE TECHBOOK
1
Committee on Assessment of Resource Needs for Fuel Cell and Hydrogen Technologies, National Research Council. Transitions to Alternative Transportation Technologies: A Focus on Hydrogen. Washington, DC: National Academies Press, 2007. 2 EIA, AEO 2009, “Energy Demand Projections,” http://www.eia.doe.gov/oiaf/aeo/demand.html, 2009. 3 By government mandate, long-haul truckers must rest for 10 hours after driving for 11 hours. During the rest periods, truckers might park at truck stops for several hours and idle their engines to provide their sleeper compartments with air conditioning or heating or to run electrical appliances such as refrigerators or televisions. 4 Greene, D. and A. Schafer, Reducing Greenhouse Gas Emissions from U.S. Transportation. Prepared for the Pew Center on Global Climate Change, 2003. 5 In turbo-charging, the intake air is compressed with some of the exhaust gas energy, which would otherwise be wasted. Thus, more air can be taken in and more engine power can be produced from a given engine size. 6 NESCCAF, ICCT, Southwest Research Institute, and TIAX, LLC. Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and CO2 Emissions. 2009. 7 U.S. DOE, Natural Gas Vehicles, 2009. 8 EPA Smartway program. 9 EIA, Annual Energy Outlook 2010. 10 These engines commonly achieve efficiencies near 50 percent, which is higher than most diesel engine applications, since ships typically operate at steady state under high load conditions. 11 U.S. DOE, Assisting Transit Agencies with Natural Gas Bus Technologies, 2005. 12 EIA, International Energy Outlook 2009, Chapter 7
Page | 9 May 2010
Transportation activity and vehicle ownership is expected to grow significantly in all countries over the next 50 years. Over the next two decades, passenger vehicle ownership is expected to double worldwide, with most of the increase occurring in non-OECD countries.
•
Passenger or light-duty vehicles are the largest source of energy consumption and greenhouse gas (GHG) emissions within the transportation sector. Medium- or heavy-duty vehicles make up many commercial vehicle fleets; these fleets consume large quantities of fuel because of intensive use and the low fuel economy of their vehicles.
•
Aircraft emissions in the United States are a small percentage of total transportation sector emissions, but are expected to grow significantly over the long term. Emissions from marine transportation are a very small percentage of current transportation sector emissions in the United States, with little domestic growth expected over the next 30 years.
Background The transportation sector consists of cars and light-duty trucks (also referred to as passenger vehicles), medium- and heavy-duty trucks, buses, trains, ships, and aircraft. Energy use and, as a result, greenhouse gas (GHG) emissions from each mode are determined by four major elements: the fuels used and their carbon content, the efficiency of each vehicle, the distance traveled, and the overall efficiency in transportation system operations (See Climate TechBook: Transportation Overview). Of the various transportation modes, passenger vehicles consume the most energy (see Figure 1). GHG emissions mirror energy use by each mode, because all modes use petroleum fuels with similar carbon contents and thus result in corresponding shares of GHG emissions. Figure 1: Transportation Energy Use by Mode (2007) Pipeline, 3.2%
Rail, 2.3%
Water, 5.6%
Air, 9.0%
Medium/heavy trucks, 18.8%
Light vehicles, 60.4%
Buses, 0.7% Source: Department of Energy (DOE), Transportation Energy Data Book, 2008.
Page | 1 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Over the next 20 years, analysts expect energy use for rail, aircraft, buses, and freight trucks to grow at higher average annual rates compared to energy use in light-duty vehicles (see Figure 2). Figure 2: Average Annual Growth in Transportation Energy Use by Mode (2008-2035) 1.4% 1.2% 1.0% 0.8% 0.6% 0.4% 0.2% 0.0%
Source: Department of Energy (DOE), Annual Energy Outlook Early Release, January 2010.
This factsheet gives a brief overview of the various transportation modes and discusses efficiency improvements available for each.
Passenger Vehicles Passenger or light-duty vehicles are defined as cars or light-trucks with a gross vehicle weight of less than 8,500 pounds. They are the largest source of energy consumption and GHG emissions within the transportation sector. Table 1: Passenger Vehicles in the United States
Cars New Vehicle Sales and Leases (Thousands, 2008) Total Vehicle Registrations (Thousands, 2007) Vehicle Miles Traveled (Millions, 2007) Average Vehicle Occupancy Rate (2006) Average Fuel Economy (2007) Average New Vehicle Fuel Economy (2008) CAFE Standard (2008)
Total
6,806
Light Trucks 6,388
135,933
101,470
237,403
1,670,994 1,111,277 1.58 1.73 22.5 31.2
18.0 23.6
27.5
22.5
13,195
2,782,271
27.0
Page | 2 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Source: Department of Transportation, Bureau of Transportation, National Transportation Statistics, 2009.
Technology options to reduce fuel consumption and GHG emissions from passenger vehicles can include the following: •
The technological improvements for light-duty vehicles can be grouped according to application: engine efficiency, transmission, and other improvements, which include vehicle weight reduction, aerodynamic improvements, and reduced rolling resistance. With full implementation of these technologies for fuel economy gains, oil consumption and GHG emissions per mile could be reduced by more than 40 percent by 2035, and about 50 percent by 2050 compared to average vehicles in 2006. 1
•
Hybrid vehicle technologies can also reduce gasoline consumption and GHG emission. There is a range of hybrid electric vehicles available today, and they are expected to make up about 20 percent of annual vehicle sales by 2015 and nearly 40 percent by 2030. 2
•
Plug-in hybrid electric and all-electric vehicles (PEVs) offer considerable improvements in engine efficiency over conventional hybrid vehicles because an electric motor can power the vehicle, in addition to the engine drivetrain. General Motors plans to deploy the first mass-produced plug-in hybrid electric vehicle, the Chevrolet Volt, in late 2010. Nissan also plans to release the first massmarket all-electric vehicle in late 2010. Key hurdles for PEVs include battery capacity, durability, and cost, as well as the infrastructure needed to charge batteries.
•
Hydrogen fuel cell vehicles produce electricity in fuel cells, which is then used to power the vehicle. Fuel cells promise a two- to three-fold increase in vehicle efficiency over conventional internal combustion engine (ICE) vehicles and emit only water vapor on use. Similar to electric vehicles, storing enough hydrogen to obtain sufficient vehicle range before refueling is a challenge, especially given the current lack of a convenient refueling infrastructure. Hydrogen vehicles can partially compensate for this problem by being significantly more efficient than ICE engines, thus requiring the storage of less on-board energy. Durability and costs of fuel cells and hydrogen production also remain challenges.
•
The passenger vehicle market has been the focus of biofuels use and research thus far. Biofuels used currently include ethanol, biodiesel, and other fuels derived from biomass. To obtain significant reductions in GHG emissions using biofuels in light-duty vehicles, a transition to advanced biofuels with significantly lower GHG emission profiles will be required. (See Climate Techbook: Biofuels Overview).
Medium- and Heavy-Duty Vehicles Vehicles in the medium-duty category have a gross vehicle weight of 8,500 to 26,000 pounds and include everything from large pick-up trucks and SUVs, small buses, cargo vans, and short-haul trucks. Heavy-duty vehicles (HDVs) have a vehicle weight over 26,000 pounds and are used in both long-distance and local transport. HDVs include long-haul trucks, large buses, and other vehicles. Medium- or heavy-duty vehicles
Page | 3 May 2010
Transportation Modes Overview CLIMATE TECHBOOK (e.g., freight and delivery trucks) make up many commercial vehicle fleets; these fleets consume large quantities of fuel because of intensive use and the low fuel economy of their vehicles.
Table 2: Medium- and Heavy-Duty Trucks in the United States, 2002
Number of Registered Vehicles
Medium‐duty trucks Heavy‐duty trucks
2,858,368 2,333,786
Percentage of Overall Truck Registrations 3.40% 2.70%
Average Average Fuel Percentage Annual Miles Economy of Overall per Truck (mpg) Truck Fuel Use 13,237 8.0 5.20% 44,581 5.8 21.60%
Source: Department of Energy (DOE), Transportation Energy Data Energy Book, 2008.
Technology options to reduce fuel consumption and GHG emissions can include the following: •
A significant amount of fuel use could be avoided by reducing vehicle idling – an average tractortrailer spends six hours each day idling to generate electricity for AC and heating systems. 3 Idle reduction technologies can include, e.g., auxiliary power units in vehicles or electrical outlets at truck stops that allow drivers to “plug in” their vehicles to operate the necessary systems. Hybrid drivetrains, similar to those used in passenger vehicles, can also help reduce idling, especially for vehicles used locally in stop and go traffic. Estimates suggest that hybrid systems have the potential to improve fuel economy by 25 to 70 percent in comparison to a standard diesel engine. 4 In the case of buses, idle reduction technologies and strategies have the co-benefit of improving air quality in areas of heavy bus use, such as schools.
•
Overall, there is less potential for improving fuel efficiency in these vehicles, compared to passenger vehicles. Most medium- and heavy-duty vehicles have turbo-charged, 5 direct-injection diesel engines, which are the most energy-efficient internal combustion engines available. State-of-the-art turbocharged diesel engines achieve 46 to 47 percent efficiency, versus only 25 percent for spark-ignited gasoline engines, which are used in most passenger vehicles in the United States. Options for improving medium- and heavy-duty vehicle efficiency include engine improvements, transmission enhancements, improved aerodynamics and changes in systems and logistics. If all these measures were fully implemented, the fuel consumption of new trucks could be reduced by 20 percent starting in 2012 and up to 50 percent in 2017. 6
•
These modes can also benefit from alternative fuel use. Lower carbon fossil fuels, such as natural gas, can reduce conventional air pollutants as well as GHG emissions. 7 For diesel-powered trucks, biodiesel blends of up to 20 percent biodiesel can be used in engines without any modification. (See Climate TechBook: Biodiesel.)
•
The U.S. Environmental Protection Agency has two programs – SmartWay Tractors and Trailers and the SmartWay Transport Partnership – which are both designed to help truck owners and freight
Page | 4 May 2010
Transportation Modes Overview CLIMATE TECHBOOK transport operators choose the most efficient vehicles and save energy and lower operating costs through improved logistics. 8
Aircraft Aircraft emissions in the United States are a small percentage of total transportation sector emissions, but are expected to grow significantly over the long term. Business-as-usual (BAU) projections for aircraft energy consumption growth in the United States are estimated at a little less than 1 percent per year over the next 25 years. 9 Table 3: Certificated Air Carrier Statistics for the United States, 2006
Number of Aircraft Aircraft‐miles (millions) Available seat‐miles (millions) Passenger‐miles (millions) Fuel consumed (million gallons) Seats per aircraft Seat‐miles per gallon Energy intensity (Btu/passenger‐mile) Load factor (percent)
Domestic operations 8,225 (2005) 6,511 742,461 591,834 13,458 114.0 55 3,070 79.0
International operations 1,428 266,725 220,138 5,827 186.8 46 3,574 79.9
Source: Department of Transportation, Bureau of Transportation, National Transportation Statistics, 2009.
A number of options are available to limit the growth in aviation GHG emissions. These include improved navigation systems in the near to medium term and advanced propulsion systems, lightweight materials, improved aerodynamics, new airframe designs, and alternative fuels over the medium to long term. •
In the near term (to 2025), the most promising strategies for improving the efficiency of aircraft operations are improvements to the aviation system: advanced communications, navigation and surveillance (CNS) and air traffic management (ATM), as opposed to changes to aircraft themselves. These improvements have the potential to decrease aircraft fuel consumption and improve aviation operations by shortening travel distances and reducing congestion in the air and on the ground.
•
Over the longer term (out to 2050), efficiency improvements can be achieved by aircraft technologies that include more efficient engines, advanced lightweight materials, and improved aerodynamics. Since aircraft have a much longer lifetime than on-road vehicles (30 to 40 years compared to an average of 14 years for a passenger vehicle in the United States), the fleet-wide penetration of advanced technologies will take a number of years. Early aircraft retirement programs might be able to push more rapid fleet turnover, but the potential benefits of such a program are uncertain.
•
The potential for fuel switching on jet aircraft is limited in the short term, compared to on-road vehicles. The only feasible options for “drop-in” replacements to petroleum-based jet fuels include hydroprocessed renewable jet fuel (HRJ) (from plants or algae) and thermochemically produced Fischer-Tropsch (FT) fuels (from biomass or fossil fuel feedstocks, if produced with carbon capture
Page | 5 May 2010
Transportation Modes Overview CLIMATE TECHBOOK and storage). Neither of these fuel production processes is commercial at this stage, and their use over the longer term also faces numerous challenges with respect to their production, distribution, cost, and the magnitude of GHG benefits that can ultimately be achieved by using them.
Marine Transportation Emissions from marine transportation are a very small percentage of current transportation sector emissions in the United States, with little domestic growth expected over the next 30 years. On the other hand, due to increases in economic activity and international trade, international marine emissions are estimated to increase by at least 50 percent over 2007 levels by 2050, under business-as-usual conditions. Table 4: Marine Transportation Statistics
Number of Vessels
Ton‐miles (billions)
Domestic Tons shipped (millions)
41,109
562
1,024
Domestics Tons shipped as percentage of total 39.6
Average length of haul (miles)
Energy intensity (Btu/ton‐ mile)
Energy use (trillion Btu)
548.7
513
288.1
Source: Department of Energy (DOE), Transportation Energy Data Energy Book, 2008.
The majority of marine vessels used for commercial operations are powered by highly efficient diesel engines. 10 These engines generally have a longer lifetime than those used in on-road transportation (30 years or more); thus, technical improvements to new engines might not reduce emissions in the shorter term. •
Immediate reductions in GHG emissions from marine vessels are available by simply reducing speed. However, reducing speed also reduces shipping capacity. To maintain shipping supply, more frequent trips or increasing ship utilization (the load factor) would be required. Although more frequent trips could increase GHG emissions, reductions in shipping supply from reduced speeds can also be countered by increasing port efficiency and optimizing land-side inter-modal transport systems, allowing for faster ship turnaround times.
•
Additional optimization of shipping logistics, routing and maintenance could reduce GHG emissions from shipping. These improvements include increased ship utilization (increased load factor), improved and more consistent maintenance practices, optimized ship control, and route planning optimized for current weather conditions and ocean currents.
•
Technological mitigation options for new ships, aside from alternative fuels and power, include larger ship sizes, hull and propeller optimization, more efficient engines and novel low-resistance hull coatings. Improvements in engine design include a more flexible design utilizing a series of smaller diesel-electric engines, each optimized for a single speed, that power an electric drive.
•
In the marine sector, most alternative energy sources currently in use or under development for application in other sectors could be applied to ships as well. Substituting marine diesel oil or liquefied natural gas for heavy fuel oil (i.e., residual fuel oil) currently used in ships can achieve GHG reductions. Other alternative fuel and power sources, such as biofuels, solar photovoltaic cells, and fuel cells, are longer-term options. Page | 6 May 2010
Transportation Modes Overview CLIMATE TECHBOOK Other Modes Rail transportation and buses are a very small percentage of current transportation sector emissions in the United States, yet growth rates for energy consumption within these modes are expected to be higher than that for other modes, with the exception of freight trucks. The rail transportation system is used for both freight and passenger travel. Passenger travel includes intercity, transit, and commuter rail systems. Buses are also used for transit and intercity travel, as well as for school transportation. In the future, these modes could make use of technological advances in other sectors, such as improvements in diesel engine efficiency, hybrid technologies, and alternative fuels. For example, many metropolitan transit systems are transitioning to natural gas buses. In 2004, about 12 percent of transit buses were powered by natural gas, and since then many transit systems have increased their natural gas bus fleets. 11
Global Context Transportation activity and vehicle ownership is expected to grow significantly in all countries over the next 50 years. Over the next two decades, passenger vehicle ownership is expected to double worldwide, with most of the increase occurring in non-OECD countries. The use of air travel and marine shipping is also expected to increase rapidly, with faster growth rates outside of the United States. Many of the non-OECD economies are predicted to experience rapid growth in energy consumption as transportation systems are modernized and the demand for personal motor vehicle ownership increases due to higher per capita incomes. Under business-as-usual conditions, non-OECD transportation energy use is expected to increase by an average of 2.7 percent per year from 2006 to 2030, compared with an average of 0.3 percent per year for transportation energy consumption in the OECD countries. 12
Policy Options A range of policy options is available for reducing GHG emissions from these various modes of transportation. Policies can include pricing policies, fuel economy or GHG emission standards, and funding for technology R&D. •
Pricing policy options include feebates, taxes on inefficient vehicles, and tax credits for purchase of fuel-efficient vehicles. A feebate can be formulated in terms of fuel economy (fuel consumption per unit distance) or GHG emissions. The manufacturer (or the purchaser) pays a fee for any vehicles produced (or purchased) that are less efficient than the target level for fuel economy or GHG emissions. The purchasers of any vehicle produced or sold that is more efficient than the target receive a rebate. The value of the fee or rebate can increase in proportion to the divergence from the targeted value. The feebate changes the initial purchase price of a vehicle, which can have a larger impact on consumer decisions than the savings from higher fuel economy alone.
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In the United States and worldwide, vehicle standards have been the main mechanism for improving the efficiency of passenger vehicles. Vehicle fuel economy standards can be expressed in miles per gallon (mpg) or kilometers per liter (km/l). Vehicle emissions standards limit GHG emissions from a vehicle and are typically expressed as grams of CO2 equivalent per kilometer (gCO2e/km).
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For other modes of transportation, low sales volumes and varied product configurations and applications make it difficult to set standards. For example, in the United States, annual sales in the heavy-duty sector are less than five percent of the annual light-duty vehicle sales. These modes can benefit from programs that quantify and create incentives for operators to use the most efficient equipment and operations. For example, EPA’s SmartWay Transport Partnership works with freight
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Transportation Modes Overview CLIMATE TECHBOOK •
truck operators to monitor and reduce fuel consumption, GHG emissions, and air pollutants. Similar efforts can be directed to other modes, such as metropolitan areas with large bus fleets. Policies to address GHG emissions from international aviation and marine shipping are especially challenging, because they are produced along routes where no single nation has regulatory authority. Two broad policy options are available for controlling emissions from international transportation: continuing work under the International Civil Aviation Organization and International Marine Organization to construct an international agreement for addressing these emissions; or assigning responsibility for these emissions to parties for inclusion in national commitments to reducing GHG emission.
Related Business Environmental Leadership Council (BELC) Company Activities • • • • • • •
Boeing Daimler Deere and Company GE Lockheed Martin Toyota United Technologies
Related Pew Center Resources Aviation and Marine Transportation: GHG Mitigation Potential and Challenges, 2009 Policies to Reduce Emissions from the Transportation Sector, 2008 Reducing Greenhouse Gas Emissions from U.S. Transportation, 2003 Federal Vehicle Standards Comparison of Passenger Vehicle Fuel Economy and GHG Emission Standards around the World Map: State Vehicle Greenhouse Gas Emissions Standards
Further Reading / Additional Resources U.S. Department of Energy, Alternative and Advanced Vehicles U.S. Department of Transportation, National Transportation Statistics
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Transportation Modes Overview CLIMATE TECHBOOK
1
Committee on Assessment of Resource Needs for Fuel Cell and Hydrogen Technologies, National Research Council. Transitions to Alternative Transportation Technologies: A Focus on Hydrogen. Washington, DC: National Academies Press, 2007. 2 EIA, AEO 2009, “Energy Demand Projections,” http://www.eia.doe.gov/oiaf/aeo/demand.html, 2009. 3 By government mandate, long-haul truckers must rest for 10 hours after driving for 11 hours. During the rest periods, truckers might park at truck stops for several hours and idle their engines to provide their sleeper compartments with air conditioning or heating or to run electrical appliances such as refrigerators or televisions. 4 Greene, D. and A. Schafer, Reducing Greenhouse Gas Emissions from U.S. Transportation. Prepared for the Pew Center on Global Climate Change, 2003. 5 In turbo-charging, the intake air is compressed with some of the exhaust gas energy, which would otherwise be wasted. Thus, more air can be taken in and more engine power can be produced from a given engine size. 6 NESCCAF, ICCT, Southwest Research Institute, and TIAX, LLC. Reducing Heavy-Duty Long Haul Combination Truck Fuel Consumption and CO2 Emissions. 2009. 7 U.S. DOE, Natural Gas Vehicles, 2009. 8 EPA Smartway program. 9 EIA, Annual Energy Outlook 2010. 10 These engines commonly achieve efficiencies near 50 percent, which is higher than most diesel engine applications, since ships typically operate at steady state under high load conditions. 11 U.S. DOE, Assisting Transit Agencies with Natural Gas Bus Technologies, 2005. 12 EIA, International Energy Outlook 2009, Chapter 7
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