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5. Transportation Sector


Energy use in the transportation sector is primarily for passenger travel and freight movements. Passenger travel vehicles consist of light-duty vehicles (automobiles, motorcycles, and light trucks) and high-duty vehicles (buses, airplanes, boats, and trains). The freight modes of transport include truck, air, rail, pipeline, and marine (domestic barge and cargo). Energy is also used for military operations and off-highway vehicles used for construction and farming.

Petroleum supplies the vehicles in the transportation sector in the forms of gasoline, diesel fuel, liquefied petroleum gas, jet fuel, and residual fuel oil. In 1992, more than 60 percent of petroleum products supplied was gasoline. The transportation sector uses very small amounts of other fuels such as natural gas and electricity.(31)

In the late 1970's total energy consumption (indexed to 1980) grew faster than Gross Domestic Purchases (GDP).(32) This pattern reversed in the early 1980's and became even more pronounced as GDP grew at a faster rate than total energy consumption. However, total energy consumption increased as well, as Figure 5.1 shows. Passenger miles have increased 21 percent between 1977 and 1992. Populations have increased and people are traveling more as the distance between work and home has increased. More shipping is being done over greater distances.(33)

The price of energy during this time was very volatile. Between 1977 and 1980, the real price of crude oil nearly doubled. It reached a peak in 1982 and then dived below the prices of the late 1970's.

Chapter Organization

The first presentation will be a detailed discussion of the several data sources used for the analysis in this chapter. This will be followed by a discussion of energy consumption in the transportation sector as a whole.

The next sections will first discuss U.S. passenger transportation followed by a discussion on U.S. freight transportation the topics presented are: energy consumption, demand indicators, and the development of energy-intensity indicators. This presentation will be followed by the development of a composite energy-intensity indicator for the entire transportation sector. The chapter will end with a discussion of the strengths and limitations of the energy-intensity indicators presented in the chapter.

Major Data Sources

U.S. Department of Energy (DOE)

Energy Information Administration

Residential Transportation Energy Consumption Survey (RTECS). The RTECS is a national multistage probability sample survey conducted on personal vehicles from a subsample of households in the RECS sample from the previous year. The first annual RTECS was conducted in 1983 with subsequent surveys conducted in 1985 and triennially thereafter. Baseline information about the RTECS household and vehicle stock is collected during the RECS personal interview. Via telephone interviews, the data for the following year are collected at two points in time about vehicle stock, vehicle stock turnover, new purchases, and vehicle-miles traveled (VMT). A third interview takes place early the following year. The RTECS is designed to collect actual VMT for each vehicle in the household by obtaining the odometer reading at two points in time. The vehicle characteristic information is collected directly from the respondents and the decoded Vehicle Identification Number. Vehicle fuel consumption and expenditures are estimated using vehicle fuel efficiency, presented in miles per gallon from the U.S. Environmental Protection Agency and adjusted for in-road degradation, and motor fuel prices from the Department of Commerce, Bureau of Labor Statistics, and Lundberg, Inc.

Oak Ridge National Laboratory (ORNL)

Transportation Energy Data Book: Transportation Energy Data Book, Edition 14 and earlier reports. These reports are statistical compendiums prepared and published by ORNL under contract with the Office of Transportation Technologies in DOE. The data book presents statistics and information from diverse sources that characterize transportation activity and presents data on other factors that influence transportation energy use.

U.S. Department of Transportation (DOT)

Bureau of Transportation Statistics

Transportation Statistics: Annual Report 1993 and Transportation Statistics: Annual Report 1994. These two reports summarize the state of the transportation system as to : the transportation network, the use of the system, how well it works, costs of transportation, safety, and energy and the environment. The data presented are from various agencies, including the U.S. Department of Commerce-Bureau of the Census, U.S. Department of Labor-Bureau of Labor Statistics, Eno Transportation Foundation, Oak Ridge National Laboratory, and the Department of Transportation-Federal Aviation Administration and Federal Highway Administration.

Federal Highway Administration

Nationwide Personal Transportation Survey (NPTS) is a periodic survey of personal travel. The NTPS data are based on a nationally representative sample of households from which the amount and nature of personal travel by all modes is collected.

Energy Consumption in the Transportation Sector


In 1992, 27 percent of total primary energy and 37 percent of total site energy was used by the transportation sector. Automobiles--both private and business--used 40 percent of the sector's energy, and trucks--light-duty and heavy-duty--used 32.7 percent (Figure 5.2).

In this chapter, only the conventional sources of energy used in the transportation sector are included in the analysis. These are gasoline, diesel fuel oil, jet fuel, residual fuel oil, and natural gas and electricity used for pipelines and light rail. Other energy sources used in the transportation sector are not included in this chapter--methanol, ethanol, liquefied petroleum gas, compressed natural gas, and other alternative fuels that are beginning to contribute to the transportation supply mix. The Energy Information Administration is just beginning to provide data related to these alternative fuels.(34)

Choice of fuel varies by transportation mode, e.g., automobiles consume gasoline, diesel, and alternative fuels; trucks run on diesel fuel, gasoline, and liquefied petroleum gas; aircraft fly with jet fuel and aviation gasoline; and marine vessels burn distillate and residual fuel oil.

Energy Trends

Almost 70 percent of the energy used in the transportation sector is used by passenger modes of travel. The smallest amount is used by the military and for off-highway vehicles such as those used in construction and farming (Figure 5.3). (35)

The two time intervals used in this chapter are one of growth/growth (1985 to 1988) and one of growth/recession (1988 to 1991). Site energy consumption grew by 8.4 percent during the interval of growth/growth, but was essentially flat (actually, 0.4 percent decline), during the interval of growth/recession (Figure 5.4).

Although most of the energy used in this sector is for passenger travel, the energy used for freight transportation grew twice as fast as that for passenger travel during the interval of growth/growth.

The passenger and freight transportation sectors are very different. Each uses different energy sources and displays different reactions to price changes. The energy efficiency characteristics of each are treated separately in the next two sections.(36)

U.S. Domestic Passenger Transportation


When the United States recognized the hazards of its dependency on foreign oil supplies in the aftermath of the first oil embargo in 1973, passenger automobile fuel economy averaged only 14 miles per gallon (mpg). Congress responded by passing the Energy Policy and Conservation Act of 1975 (Public Law 163), which established Corporate Average Fuel Economy (CAFE) standards for each automaker, with domestically produced and imported automobiles counted as separate fleets.(37) The uniform CAFE standard for automobiles began at 18 mpg with the 1978 model year, increasing to 27.5 mpg by 1985. For trucks, the CAFE standard began at 17.2 mpg in 1979, rising to 20.5 mpg by 1987.

Public agreement as to the success of the CAFE standards is still pending. During the time when most of the standards were coming into effect, the price of gasoline was sharply increasing. The price increases could have increased the public demand for more efficient automobiles. Nevertheless, vehicle fuel efficiencies have increased. Newer automobiles are more efficient than older cars, averaging 20.6 to 22.0 mpg for model year 1983 or later compared with 14.1 mpg or less for model year 1979 or earlier.(38)

Passenger Transportation Energy Consumption

Site energy used for domestic passenger travel increased by 6 percent during the growth/growth interval and decreased by almost 2 percent during growth/recession interval (Figure 5.4). Automobiles and light trucks are responsible for most of the energy consumed in passenger transportation (Figure 5.5). The total site energy used in light trucks grew the most of any of the passenger modes during the growth/growth interval (13.2 percent) (Figure 5.6).

All passenger transportation modes except mass transit sustained reductions in energy use during the growth/recession interval.(39) In fact, mass transit energy use, which accounted for no more than 1 percent of passenger site energy consumption in 1991, increased throughout both intervals of time, despite recent survey results showing increased preference for personal vehicles at the expense of mass transit.(40)

The mode experiencing the smallest decline in site energy consumption during the growth/recession interval was light trucks. The increased penetration of light trucks with lower fuel economies than passenger automobiles may be responsible for this.(41)

Three modes--general aviation, air carriers, and motorcycles--experienced large percentage reductions in site energy use during the growth/recession interval; however, these three modes combined amount to about 10 percent of passenger site transportation energy use. Air carrier energy use grew by 7 percent during the growth/growth interval, only to shrink by an equivalent amount during the growth/recession interval.

Demand Indicators

A number of possible demand indicators may be considered as drivers of the demand for energy services in the passenger transportation sector. None of these indicators is universally applicable to all passenger transport modes:

  • Population growth is indicative of the demand for personal or household vehicles, and indirectly for nonresidential vehicles to support the economy
  • Number of persons working may serve as a good indicator of the demand for business travel, either commuting daily by car, bus or rail, or extended business trips by rail or air
  • Number of vehicles in each mode is useful for within modes perhaps, but not across modes. It severely restricts analysis of high-density vehicles (i.e., buses, trains, and planes carrying more people per vehicle)
  • Growth in personal income is an important indicator because in the residential transportation sector, higher incomes are more likely to result in the purchase of a second or third car. In 1991, for every additional $16,000 of income, vehicle miles traveled increased by approximately 3,000 miles (42)
  • Number, frequency, and duration of trips made by passenger vehicles vary significantly. For example, in 1991, the average car trip was 9 miles while buses averaged 143 miles and planes 806 miles per trip (43)
  • Fuel cost is considered to be a key determinant of transportation demand--the low price of gasoline, which contributes to low overall vehicle operating costs, currently does not appear to be as influential in consumers' choice of vehicle purchases in comparison with the 1970's and early 1980's (44)
  • Vehicle-miles traveled mask differences in vehicle occupancy across passenger transport modes and changes in occupancy over time--in 1991, automobiles carried on average 1.6 passengers per mile while buses and air carriers transported 16.4 and 87.7 passengers, respectively
  • Passenger-miles traveled reflects vehicle occupancy within each passenger mode--in 1991 mass transit rail and buses traveled more than 12 billion vehicle-miles, compared with 153 billion passenger-miles over the same period.

Trends in Demand Indicators

While the vehicle may be the consuming unit, the energy-service demand is for movement from one point to another--distance traveled or a social interpretation would say, 1 trip. Only two of the above indicators include distance, Vehicle-Miles Traveled (VMT) and passenger-miles traveled (PMT).

Vehicle-Miles Traveled

VMT grew significantly during 1985-1991 (Figure 5.7). and (Figure 5.8)), primarily because of the growth in VMT for light-duty vehicles (23 percent). Most of this growth took place during the growth/growth interval (Figure 5.8a). Of all of the light-duty vehicles, the light truck experienced the largest growth in VMT, not only for the growth/growth interval, but even larger growth during the growth/recession interval.

The mix of light-duty vehicles has changed substantially since 1985. Automobiles, while still dominant, lost a 6-percent share among all light-duty vehicles: 72 percent in 1991 compared with 78 percent of all light-duty vehicles in 1985. Minivans, which were just entering the market in 1985, have made substantial market penetration, exceeding 5 million vehicles in 1991, or a 3-percent market share. Sport-utility vehicles doubled within these 6 years, from 3.7 million to 7.3 million vehicles in 1991. Pickup trucks increased in number to almost 26 million vehicles in 1991.

VMT for high-duty vehicles showed a 11-percent growth during the growth/growth interval and only a 3-percent growth during the growth/recession interval. Air carriers experienced the largest growth in VMT during the first interval (22 percent).

A number of factors are responsible for growth in VMT:

  • Increasing driving-age population
  • Growing working population, as more women enter the workforce and more families have two income-earners
  • Rising real income levels, which make airfares and extended trips more affordable
  • Rising demand for travel as lifestyles become more multi-dimensional
  • Increasing average personal trip length (9-percent increase between 1983 and 1990) for almost all purposes (45)
  • Longer commutes as more homes are located outside of central cities.(46)
  • Lower vehicle occupancy, which increases vehicle miles relative to PMT (Figure 5.9).

Passenger-Miles Traveled

Most of the growth in PMT can be attributed to light-duty vehicles (Figure 5.10). In 1991, there were 3.5 trillion passenger miles, of which 2.5 trillion were attributed to automobiles. The number of PMT has continually climbed over both the growth/growth interval (11.8 percent) and the growth/recession interval (5.4 percent). The increasing choice of consumers for light trucks and air travel is reflected in high increases in PMT by these two modes (Figure 5.11).(47)

PMT by light trucks increased 17 percent during the growth/growth interval, almost twice the rate of increase for automobile passenger miles. Over the next 3 years, light-truck passenger miles grew by 6.9 percent, a rate of growth only slightly greater than automotive passenger mile growth. Passenger demand for automobiles and light trucks buoyed an otherwise flat recessionary period.

Most of the increases in heavy-duty vehicle use took place during the growth/growth interval. Passenger demand for air carriers and mass transit grew by 20 percent and 17 percent, respectively, during these two intervals. PMT by these three modes did not increase noticeably over the growth/recession interval.

Passenger Transportation Energy-Intensity Indicators

Two energy-intensity indicators are presented in this section: VMT and PMT. VMT does not take into account the number of passengers in a vehicle. Only detailed data on light-duty vehicles used by households, are available from the RTECS conducted by EIA.

PMT accounts for differences in vehicle use and occupancy. These indicators are presented separately so as not to encourage comparisons. The two different indicators are based on two different data sets and vehicle definitions. The RTECS data, the source for VMT, cover only household vehicles. The data set used for PMT (DOT) defines vehicles differently, e.g., light trucks are both household and commercial vehicles. Additionally, DOT defines light trucks as any 2-axle or 4-tire truck, whereas, EIA's definition is based on weight.

Trends in Energy-Intensity Indicators

Energy per Vehicle-Mile Traveled

In 1991, the passenger car displayed the lowest energy-intensity indicator of all of the household vehicles, 5.9 thousand Btu per VMT. The largest was the large van (9.1 thousand Btu per VMT). In 1991 the sport-utility intensity indicator was 7.9 thousand Btu per VMT versus 5.9 thousand Btu per VMT for the passenger car(Figure 5.12 a). The largest reduction in the energy-intensity indicator has been experienced by sport-utility vehicles, a 20-percent reduction in the energy-intensity indicator between 1985 and 1991 (Figure 5.13) with most of the reduction between 1985 and 1988, the growth/growth interval. However, even with such a large reduction in the intensity indicator, sport-utility vehicles intensity indicator is still much higher than the passenger car.

Overtime, each type of passenger vehicle has experienced reductions in energy-intensity. In fact, vehicle vintage is closely associated with household vehicle energy-intensity. Newer vehicles were, on average, 12 percent less energy intensive per VMT (Figure 5.13) in 1991 then in 1985. However, the energy-intensity indicator for 4-6 year-old vehicles in 1991 is no different than that of new cars, but substantially better than the energy-intensity indicator of 4-6 year-old vehicles in 1985 (Figure 5.12). There were 31 percent fewer new household vehicles on the road in 1991, a recession year, than in 1985. Vehicles were held longer in 1991 than in 1985. The share of vehicles 4 to 6 years old increased from 19.2 percent in 1985 to 25.8 percent in 1991 (Figure 5.14).

Figure 5.14 displaying the percent share of vehicles by vehicle type and vehicle age, shows a reduction in the share of the passenger car and an increase in the share of sport-utility, pickup truck, and the new Minivan. The gas mileage for these vehicles is less than the passenger car, thus dampening the reduction in energy-intensity indicator for household vehicles as a whole.

Energy per Passenger-Mile Traveled

Among light-duty vehicles, light trucks are the most energy intensive, consuming 5.9 thousand Btu per PMT in 1991, or two-thirds more energy than an automobile, to move one passenger 1 mile (Figure 5.15). Among the high-density vehicles, general aviation vehicles are the most energy intensive, consuming 9.6 thousand Btu per PMT in 1991. Smaller general aviation planes consumed over two and one-half times more jet fuel than commercial air carriers to move one passenger 1 mile. Mass transit (buses and rail) are the least energy intensive of all modes.

During the growth/growth interval, all passenger modes except general aviation reduced their energy-intensity per PMT. Automobiles reduced their consumption of motor fuels per passenger mile by almost 6 percent (Figure 5.16). Automobile passenger miles increased far faster than automobile energy consumption during the interval, which may be correlated with stock turnovers.

Although the energy-intensity indicator for mass transit was 8 percent less intensive over the growth/growth interval, this intensity indicator grew by almost 6 percent over the growth/recession interval. Several effects may explain these changes. Buses in the United States are aging, causing energy-intensity indicators to increase. The federally recommended average of 12 years for a standard bus and 10 years for a medium-duty bus.(48)

If age is considered a surrogate for physical condition, and if deteriorating condition adversely affect intensity then the energy-intensity of the aging bus fleet will increase.

Mass transit rail cars and locomotives, stations, track, and maintenance facilities are far newer than buses. Mass transit travel is most often used in the urban areas. Urban areas are most apt to have rapid rail systems. As shown in the 1990 Nationwide Personal Transportation Survey, ridership problems face both commuter and intercity rail.

The largest reductions in the energy-intensity indicator were registered in air travel. Commercial air carriers reduced the energy- intensity of their operations by 11 percent during the growth/growth interval and by another 8 percent during the growth/recession interval. This reduction was achieved by increasing passenger miles faster than jet fuel demand during the growth/growth interval and by reducing jet fuel demand by 7 percent during the growth/recession interval while moving the same number of passenger miles. Flight stage length is a key determinant of energy-intensity.

Increasing flight stage lengths increase the overall efficiency of the aircraft by:(49)

  • Reducing the fuel used for taxing, idling, climb-out, and approaches
  • Using larger, more efficient aircraft
  • Increasing load factors if frequency of service decreases.

Fewer, more efficient aircrafts, with increased passenger loads and traveling over longer distances directly does reduce energy-intensity.

Between 1988 and 1992, the average flight-stage length has fluctuated between 563.2 miles and 588.4 miles with a slight upward trend. (50)

U.S. Domestic Freight Transportation

Background: The Changing Regulatory Environment of Freight Transportation

Rail. Much of the growth in transportation energy consumption between 1973 and 1985 was due to freight energy use. Deregulation helped increase the demand for energy from freight carriers.

Rail freight transportation in the United States has a history of regulation and subsidization. Major federal legislation passed during the 1970's and 1980's partially deregulated portions of the freight system: The Regional Rail Reorganization Act (1973) and Railroad Revitalization and Regulatory Reform Act (1976) provided financial support for bankrupt train companies and relaxed some rate regulation by the Interstate Commerce Commission. But the railroads were still considered completely regulated until the passage of the Staggers Act in 1980, which removed regulatory control of markets in which train companies faced substantial competition, and streamlined regulations relating to company mergers and track abandonment.

Trucking. In 1980, only 44 percent of trucking industry movements were regulated,(51) essentially that portion of travel under Interstate Commerce Commission control. The Motor Carrier Act of 1980 reduced restrictions on entry and expansion in the trucking industry and relaxed various regulations. The Surface Transportation Assistance Act (1982)superseded state requirements on size and weight limits for trucks.(52) The number of businesses in highway freight transportation appears to have grown since partial deregulation in 1980. The Interstate Commerce Commission reports more than 50,000 for-hire motor carriers are currently operating. It has been estimated that 74 percent of all intercity freight was carried by regulated trucks in 1991.(53)

Other freight modes. Congress deregulated domestic air cargo transport in 1978. However, the authority to block discriminatory and preferential rates was retained by the Civil Aeronautics Board until 1984, when the authority was transferred to the Department of Transportation. Oil pipelines remain 84 percent regulated by the Federal Energy Regulatory Commission. Domestic waterborne cargo is the least regulated portion of the freight industry, with only 8 percent of river and canal freight transport regulated in 1991.

Freight Transportation Energy Consumption

Freight total site energy consumption totaled 5.0 quadrillion Btu in 1991, representing approximately 23 percent of total site transportation energy (Figure 5.3). Most of the energy was used by trucks, which have access to 3.9 million miles of roads and streets throughout the U.S. highway system (Figure 5.17). For nonbulk cargo--mail, perishable foods, packaged goods--trucks are the dominant transport mode.(54)

During the growth/growth interval, site energy consumption grew from 3.9 quadrillion Btu to 4.4 quadrillion Btu (12 percent).(55) Most of the growth was in the trucking industry (13 percent). Domestic marine transportation reduced site energy consumption by 19 percent during the interval. Rail energy consumption displayed very little growth (Figure 5.18).

During the growth/recession interval, site energy consumption fell by almost 8-percent. Over both intervals of time, oil pipelines displayed a 3-percent growth in energy consumption.(56)

The changing structure of the U.S. economy has played a major role in the changing nature of freight transport. The economy is providing more higher value-added products that weigh less per dollar of value added than raw materials.(57) Air and truck carriers are transporting a growing share of these high value added products, at the expense of rail and boat transport. Moreover, intermodal freight (carriage on trailers and containers by trains, barges and ships for final delivery by trucks) is the fastest growing segment of truck freight.

Freight Transportation Demand Indicators

The freight transportation sector is a very heterogeneous sector, making it difficult to find one demand indicator that captures changes in demand for all of the various modes.

Using the number of freight vehicles as a demand indicator is inappropriate. Freight vehicles vary by size, weight, speed, age, and cost. For example, transport units include a variety of engines or self-propelled vessels (tractor trucks, locomotives, towboats, tugs, tankers, ships) and hauled or non-self-propelled vessels (rail cars and barges). In freight handling, one engine or self-propelled vessel will drag or push a number of flat hauling vehicles that by themselves do not consume energy.

Employment in rail, marine, truck, or air freight is not a perfect indicator. Employment has stayed constant or fallen since 1985.(58) Freight handling is very labor intensive at the points of origin and destination, but the need for workers during very long hauls varies by type of mode. Increasing employment in any particular freight mode would not necessarily be considered as the cause of greater energy demands, because the employee is not the consuming unit.

Economic activity is also an imperfect indicator. When the economy is growing, freight revenues increase. The opposite is true in times of economic contraction. One way of capturing economic activity is to use the industrial production index as a proxy for the demand for freight movements. This index is based on the value of output but freight energy consumption is not necessarily a function of the dollar value of manufacturing shipments or value added. Tonnage of freight hauled or miles traveled do not necessarily move in tandem with increases in the industrial production index, value of manufacturing shipments, or manufacturing value added. Shifts in the product mix that alter the industrial production index, for instance, are structural shifts in the manufacturing sector, not the source of efficiency improvements in freight transportation.

The weight of goods moved is more closely associated with the amount of energy consumed than with the value of the product transported. If more tons of cargo are moved, independent of the value of the cargo, then more energy is expended. Measuring freight movements purely in terms of weight is misleading, given the changing structure of the economy towards more lighter, higher value-added products and their domination of freight transport.

The distance the freight travels and the weight of the cargo being hauled measured in miles and tons, respectively, is correlated with energy consumption. The demand indicator, ton miles, captures both the weight of the freight and the distance it travels. Data available on intercity freight movements most likely underestimates the total amount of miles traveled since short hauls within city borders are not included.

Figure 5.19 presents a comparison of the composition of domestic freight by ton-miles traveled and transported for 1985, 1988, and 1991. In 1991 trucks hauled 42 percent of the weight but only 24 percent of the ton miles. Trucks haul primarily lighter, high-value added products shorter distances than other freight modes.

The opposite situation faces domestic marine and rail freight modes. In 1991, waterborne carriers haul only 16 percent of the total intercity freight but account for almost 25 percent of the ton-miles traveled. Rail freight moves 16 percent of the tons but accounts for over 18 percent of the ton miles traveled. Air freight tons and ton miles are comparable. Air freight represents less than 0.1 percent of the tons transported.

Trends in Freight Transportation Demand Indicator

During the growth/growth interval, ton miles grew by almost 9 percent while the growth/recessionary interval basically showed no growth. Trucks and rail both registered 15-percent gains in ton miles during the growth years with fewer gains during the growth/recession interval (Figure 5.20). Rail relies on coal and farm products for at least half of its business. For trucks, no single commodity accounts for more than 16 percent of revenues; agriculture, food, and other manufactured goods accounted for 29 percent of the 1991 revenues in the trucking industry.(59)

During the growth/growth interval, data as mentioned previously were not collected on the small package carriers until 1986, but this mode seems to be doing well as ton miles grew by almost 7 percent in the growth/recession interval. Air freight focuses on high-value goods with high-time demands, either perishables or high-value technical goods.

The largest reduction in ton miles was experienced by the domestic marine freight mode. Growth in this mode was flat during the growth/growth interval and fell by almost 11 percent during the growth/recession interval. Marine transport has traditionally hauled lower value-added, heavy cargo. An important factor that may have contributed to a reduction in domestic marine ton miles is the rise of imported goods.(60) Waterborne carriers rely on petroleum and coal for at least half of their revenue.

Oil pipeline ton miles track movements in the petroleum industry. While domestic crude oil production fell 9 percent during the growth/growth interval, imports of crude oil grew by 60 percent.(61) Refinery output increased by 9 percent during this time.(62) Ton miles grew by 7 percent since most of the refinery output is delivered to end users via the product pipeline system. During the growth/recession interval, domestic crude oil production fell by 9 percent, imported crude increased by only 13 percent, and refinery output showed very little growth. As a result, ton miles decreased by nearly 4 percent.

Freight Transportation Energy-Intensity Indicators

Only one energy-intensity indicator is presented for the freight transportation sector, energy per ton miles. The heavier the freight, and the more miles this freight is carried, the more energy is needed. If less energy is used for the same level of weight and miles or if more weight is carried and/or more miles are traveled for the same amount of energy, then gains in energy efficiency may occur depending on the level of any structural or behavioral effects that may have taken place.

When comparing the energy-intensity indicator for freight transportation, energy used for nonhauling purposes is included. For freight modes, a significant portion of the energy expended is attributed to non-haul purposes, e.g., almost half of the energy consumed by freight rail is not used to move freight:

  • More than 30 percent is used for empty backhaul
  • About 4 percent is reported lost or spilled each year
  • About 4 percent is consumed in idling
  • Ten percent is used by yard locomotives assembling and switching cars. (63)

Trends in Freight Transportation Energy-Intensity Indicators

Air freight continues to be the most energy-intensive mode of freight transportation (Figure 5.21). In 1985, air freight required 20 thousand Btu to move 1 ton 1 mile. By 1988, during an interval of growth/growth, this had climbed to 31 thousand Btu per ton mile. During the growth/recession interval, this grew more slowly to 32 thousand Btu per ton mile.

Trucks were the second most energy-intensive freight mode, requiring 4.8 thousand Btu per ton mile in 1985. During the growth/growth interval, energy consumption increases were close to that of increases in ton miles leading to approximately a 1-percent reduction in the energy-intensity indicator (Figure 5.22a). During the growth/recession interval, energy consumption growth fell slightly while ton miles increased by 8.3-percent causing a 7.9-percent decrease in the energy-intensity indicator (Figure 5.22b). Throughout the 1970's and early 1980's, there has been only modest improvement in truck-fleet economy, with combination trucks averaging 5.5 mpg and larger single-unit trucks at 7.3 mpg in 1990. Heavy single-unit trucks are twice as energy intensive as light trucks used for passenger travel. On average, a combination truck requires 3.1 thousand Btu to haul 1 ton of cargo 1 mile in 1991.(64)

Countervailing factors may have yielded small gains in truck fuel economy. Factors that may have contributed to improved fuel economy include:

  • Increased trip lengths
  • Technical improvements in electronic engine controls
  • Demand-actuated cooling fans
  • Intercoolers
  • Low-profile radial tires

The energy-intensity indicator for marine freight transportation decreased by 19 percent during the growth/growth interval, only to reverse this improvement during the growth/recession interval with a 14-percent increase in the energy-intensity indicator. During the growth/growth interval, much of the decrease resulted from a substantial reduction in consumption (19.4 percent) while the energy-intensity increase during the growth/recession interval was due to a large decrease in ton miles (10.5 percent). Increased imports reduced the distances that domestic marine freight has to travel. The hauling of raw materials and manufactured products which has traditionally been the domain of rail and marine freight, and any intermodal competition has significantly been reduced.

The following improvements in technology and engineering may lead to reductions in the marine freight energy-intensity indicator:

  • Improved engines, with greater use of fuel management computer systems
  • Improved matching of barges and tugs
  • Improved computer-aided operations
  • Improved channels and locks
  • Use of larger barges and tugs.(66)

Marine carriers are more energy intensive per ton mile than freight trains carriers because the density and viscosity of the water are greater than those of air. A 10-percent reduction in marine operating speeds will yield a 20-percent reduction in energy use.(67)

The energy-intensity indicator for freight trains decreased by 12 percent for each of the two intervals, growth/growth and growth/recession. In both cases, the decreases in the energy-intensity indicator were due to growth in ton miles. At the same time, energy consumption experienced slow growth (1.3 percent) during the growth years and energy consumption fell (7.6 percent) during the growth/recession interval.

Several rail efficiency improvements may be responsible for this reduction:

  • Increased average trip length with fewer
  • stops and greater sustained speeds
  • Improved operations and communications--routing, scheduling, reduced empty car-miles, minimized starts and stops, and better matched locomotives and loads

Technical improvements--reduced locomotive idling speeds, improved sizing of auxiliary loads, improved wheel-slip detection, greater use of flange lubricators, weight reduction, and aerodynamic improvements.(68)

The oil pipeline energy-intensity indicator decreased during the growth/growth interval (increase in ton miles larger than increase in consumption), only to increase during the growth/recession interval (energy consumption increased while ton miles fell). In most cases, there are no cheap alternatives to pipeline freight. Consequently, pipelines have encountered relatively little competition from other freight modes.

Transportation Energy-Intensity Composite Indicator

It is very difficult to make meaningful comparisons across passenger and freight modes. While both modes are petroleum dependent, passenger modes are dominated by gasoline-fueled internal combustion engines, and freight modes are dominated by diesel engines. Since there is no common demand indicator that may be used for the entire transportation sector, the percent change in the energy-intensity indicators from both passenger and freight travel is used in a transportation sector energy-intensity composite indicator. A multiplying factor is used that takes into account the relative share of site energy consumption of both passenger and freight modes.(69) Two composite energy-intensity indicators are presented. The first composite is a "bottom-up" approach that is built up from the individual passenger and freight modes. The second composite is a "macro" approach calculated from macro passenger and freight sums.(70)

Table 5.1 shows the shares of each mode as a percent of total site transportation energy. In both cases, appropriate energy shares for the later year in any time interval were used. In this analysis, both composite energy-intensity indicators produce similar results, whether the methodology was micro or macro. Over the interval of growth/growth, energy-intensity composites show a decrease of 3.4 percent for the micro-transportation composite and 3.6. percent for the micro-transportation composite, implying an overall increase in energy efficiency. For the interval of growth/recession, the energy-intensity composites also suggesting that there may be an overall increase in energy efficiency, keeping in mind possible other structural and behavioral effect that could be affecting the results.

Table 5.1. Building up a Composite Energy-Intensity Indicator for the Transportation Sector

Passenger and Freight Modes Percent Share of Energy Percent Change in Intensity
1988 1991 1985 to 1988 1988 to 1991 1985 to 1991
Automobiles 41.0 40.6 -5.5 -6.9 -12.0
Motorcycles 0.1 0.1 -3.7 -0.3 -3.9
Light Trucks 18.8 18.7 -3.3 -7.1 -10.1
General Aviation 0.7 0.6 0.7 -18.9 -18.4
Air Carriers 6.0 5.6 -10.9 -8.1 -18.1
Buses 0.7 0.8 -12.4 9.2 -4.4
Passenger Rail 0.2 0.2 -4.9 2.7 -2.3
Freight Trucks 15.1 15.2 -1.4 -7.9 -9.1
Air Freight a 1.3 1.4 54.5 2.1 57.7
Marine Freight 1.5 1.5 -19.1 13.8 -7.9
Rail Freight 2.0 1.8 -11.8 -11.8 -22.3
Oil Pipeline 0.1 0.1 -8.6 9.5 0.1
Micro-Transportation Composite 100.0 100.0 -3.6 -5.8 -9.0
Light-Duty Passenger Vehicles 60.0 59.5 4.2 -6.9 -10.8
Heavy-Density Passenger Vehicles 7.6 7.2 -9.7 -7.1 -16.1
Freight Trucks 15.1 15.2 -1.4 -7.9 -9.1
Non-Highway Freight 4.8 4.9 1.1 2.7 3.8
Macro-Transportation Composite 100.0 100.0 -3.4 -5.7 -8.8
aAir Freight estimate increased after 1985 because data collection of small packages shipments did not begin until 1986.

Sources: Department of Energy, Oak Ridge National Laboratory (ORNL), Transportation Energy Data Book: Editions 11 and 14, Table 2.6 and unpublished 1985 data from ORNL. U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics, Annual Report (September 1993), Table 6, and earlier publications.

Strengths and Limitations of the Indicators

A strength of the indicators for both passenger and freight transportation modes is that they depend on the energy content of the fuel being used. This allows all types of fuel to be evaluated and compared. When alternative fuels develop a significant presence in the fuel mix, the analysis used will still apply.

The analysis excluded several modes of both passenger and freight transportation. Off-highway energy use, recreational boats, cruise ships, military energy use, natural gas pipelines, and foreign air travel and water cargo were not analyzed because of lack of available demand indicators.

Data on the miles traveled and energy used to move passengers and freight are at times imprecise and contradictory. The Office of Technology Assessment identified two main reasons for the discrepancies: (1) inconsistent definitions on weight class, personal use, intercity movements, and inclusion of government and military vehicles; and (2) inconsistent data collection and quality (critical data are extrapolated from limited sample surveys or added from questionable State estimates).

In the study, Transportation Energy Efficiency Trends 1972-1992, limitations of the data are presented including:

  • Truck freight ton miles are not reported for all types of trucks.
  • Pipeline ton miles are not reported annually for natural gas.
  • Domestic waterborne transport data fluctuate.
  • Passenger-mile data are interpolated from infrequent surveys.

Data are weak in assessing significant changes in the trucking industry since deregulation. The Motor Freight and Warehousing Census tracks trucking performed only by firms engaged in trucking services, excluding the majority of the trucking industry: owner-operator trucking, and corporate truck fleets that haul their own goods.(71) Since deregulation, private fleets provide for-hire services, freight forwarders own their own fleets, and railroads and air carriers increasingly own and operate their own trucking fleets.

EIA's definition of light trucks may have affected the estimate of energy usage for this category. The definition of light trucks as used by the Eno Transportation Foundation is consistent with the Department of Transportation definition--all 2-axle, 4-tire single-unit trucks. However, EIA defines light trucks as trucks weighing up to 8,500 pounds. About 99.9 percent of the light trucks in the RTECS weighs 8,500 pounds or less. Since some 2-axle 4-tire trucks weigh substantially more than 8,500 pounds, the energy used for light trucks may have been overestimated.

End Notes

31As of December 1992, there were 2,240 federal and over 248,000 nonfederal alternative-fuel vehicles. Almost 143 million automobiles and 43 million light trucks were operated on alternative fuels in the United States in 1991. These 250,240 alternative-fuel vehicles represent less than 0.2 percent of the passenger vehicles. See Alternatives to Traditional Transportation Fuels: An Overview, DOE/EIA-0585/O (June 1984) for more detailed information.

32Gross Domestic Purchases includes imports and excludes exports.

33For more information, see "Transportation and its Costs" in Transportation Statistics: Annual Report 1994, U.S. Department of Transportation, Bureau of Transportation Statistics.

34The pilot study of alternative fuel vehicles in Atlanta is the first computer-assisted telephone interview survey of participants in the Clean Cities program co-sponsored by the U.S. Department of Energy and the U.S. Environmental Protection Agency.

35In this chapter, passenger vehicles do not include recreational boats. Freight transportation modes do not include foreign air and marine cargo movements. Military transportation and other vehicles such as construction and farm vehicles are excluded as well. Marine freight does include domestic movements through canals, rivers, the Great Lakes, and along the coasts.

36See Green, David L. And Yuehui Fan, Transportation Energy Efficiency Trends, 1972-1992, Oak Ridge National Laboratory (December 1994) for a detailed discussion of energy efficiency in the transportation sector.

37Fleet CAFE values are measured as the sales-weighted harmonic mean of individual model fuel economies. These standards are based on tests administered by the U.S. Environmental Protection Agency; actual on-road fuel economy is considerably less. CAFE standards for light trucks are lower than for passenger cars. See Office of Technology Assessment, Improving Automobile Fuel Economy: New Standards, New Approaches, OTA-E-504 (October 1991, for more information.

38See Chapter 4, "Vehicle Fuel Efficiency and Consumption," in Household Vehicles Energy Consumption 1991 (DOE/EIA-0464(91)) for further information.

39Since rail and bus transit vehicles consume energy whether people board them at full capacity or not, increases in energy use may not necessarily signify greater passenger occupancy aboard mass transit.

40U.S. Department of Transportation, Federal Highway Administration, Nationwide Personal Transportation Survey: Travel Behavior Issues in the 90's.

41Different CAFE standards apply to trucks and automobiles.

42See EIA's Household Vehicles Energy Consumption 1991, p. 19. (December 1993), (DOE/EIA-0464(91)).

43U.S. Department of Transportation, Bureau of Transportation Statistics, 1990 Nationwide Personal Transportation Survey, Summary of Travel Trends, p. 18; Eno Transportation Foundation, Transportation in America 1994, p. 70.

44U.S. Congress, Office of Technology Assessment, Improving Automobile Fuel Economy: New Standards, New Approaches, OTA-E-504 (Washington, DC: U.S. Government Printing Office, October 1991), p. 2.

45U.S. Department of Transportation, Federal Highway Administration, Nationwide Personal Transportation Survey: Summary of Travel Trends, pp. 33 and 42. The NPTS was conducted in 1983 and 1990.

46This could be mitigated somewhat, by the growth of homes and businesses in the suburbs which would imply shorter commutes.

47Light trucks include Minivans, sport-utility vehicles, and pickup trucks. See the definition of "Light Truck" in the transportation section of the Glossary.

48U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics, Annual Report 1994, (January 1994), Table 2-8, p. 30.

49A.B. Rose, Energy-Intensity and Related Parameters of Selected Transportation Modes: Passenger Movements, ORNL-5506 (Oak Ridge, TN: Oak Ridge National Laboratory, January 1979), pp. 3 and 4.

50U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics: Annual Report 1994, pp. 83 and 84.

51The percentages are calculated from the portion of freight ton miles carried by the mode. See Eno Transportation Foundation,Transportation in America 1994, pp. 17 and 51.

52U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, p. 50.

53U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics: Annual Report 1994, pp. 19 and 20.

54U.S. Department of Transportation, Federal Highway Administration, Highway Statistics 1991, Tables MV-9 and MV-11.

55Excluding energy for moving water and natural gas.

56Pipelines include those moving crude oil, petroleum product, coal slurry, natural gas, and water. This chapter is limited to oil pipelines, since comparable demand indicator data are not available for natural gas.

57U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington DC: U.S. Government Printing Office, July 1994), p. 50.

58U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics, Annual Report (September 1993), Table 57, p. 144.

59U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington, DC: U.S. Government Printing Office, July 1994), pp. 43-46. These pages present a discussion on the types of goods each of the freight modes carry.

60U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington, DC: U.S. Government Printing Office, July 1994), p. 50.

61U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, Annual Energy Review 1993, Tables 5.2 and 5.3, pp. 143 and 145.

62U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, Annual Energy Review 1993, Table 5.8, p. 155.

63A.B. Rose, Energy Intensity and Related Parameters of Selected Transportation Modes: Freight Movements, ORNL-5554 (Oak Ridge, TN: Oak Ridge National Laboratory, June 1979), pp. S-10 and 5-4.

64Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics: Annual Report 1994, p. 153.

65U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington, DC: U.S. Government Printing Office, July 1994), p. 51.

66U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington, DC: U.S. Government Printing Office, July 1994), pp. 52 and 53.

67A.B. Rose, Energy Intensity and Related Parameters of Selected Transportation Modes: Freight Movements, ORNL-5554 (Oak Ridge, TN: Oak Ridge National Laboratory, June 1979), pp. 4-2 and 4-3.

68U.S. Congress, Office of Technology Assessment, Saving Energy in U.S. Transportation, OTA-ETI-589 (Washington, DC: U.S. Government Printing Office, July 1994), p. 52 cites Abacus Technology report without full citation.

69In Chapter 7, "Economy," the methodology for the economy composite is presented. The methodology is basically the same as presented here.

70The more detailed "Micro-Transportation" indicator is the more robust of the two indicators. This is because the more structural and behavioral effects that could be included before the build up of to the composite, the greater the chance that such effects will be removed.

71U.S. Department of Transportation, Bureau of Transportation Statistics, Transportation Statistics: Annual Report 1994, p. 61.

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