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Amtrak and Energy Conservation in Intercity Passenger Transportation

Stephen J Thompson
Specialist in Transportation
Economics Division

Updated September 3, 1996

96-22 E


A rationale for federal financial support to Amtrak has been that rail service conserves energy, compared to other forms of intercity passenger transportation.(l)(2) The numbers presented in this report suggest that the rationale might not be valid with regard to some alternative modes of transportation, and the report discusses some public policy implications that could follow from that conclusion.


The fuel intensity of alternative modes of intercity passenger travel is contained in table 1.(3) As can be seen from the numbers there, intercity buses use less than 40% of the energy of Amtrak (measured in Btu(4)) per passenger-mile. Automobile trips longer than 75 miles are about as energy efficient as travel by Amtrak, and the average trip length on Amtrak in fiscal year 1995 was 257 miles.(5) Transportation by certificated air carriers on domestic routes consumes substantially more Btu than Amtrak, and general aviation uses more than three times as much energy as Amtrak.

TABLE 1. Fuel Intensity of Competing Modes of Intercity Passenger Transportation
(in ascending order of Btu consumption per passenger-mile)

Mode of Transportation Btu per Passenger-Mile Btu per Pass.-Mile Compared to Amtrak
Intercity buses 953 36 %
Autos, trips over 75 miles 2,625 99
Amtrak 2,646 100
Autos, all trips, including local 3,593 136
Air, certificated route, domestic 4,482 169
Air, general aviation 8,582 324

Note: The appendix cites the sources for this table, gives the derivation of the Btu number for auto trips over 75 miles, and shows the sensitivity of that number to a change in the average number of occupants on such trips. The derivation of the number for each of the other categories is provided in the U.S. Department of Energy source cited in the appendix, and each number is based on the average load factor for that category.

However, as an Office of Technology Assessment (OTA) report states, "[T]he energy intensity of the vehicles tells a limited story, since a great deal of energy is imbedded in each mode's capital infrastructure and expended in ancillary activities such as powering stations, repairing roadways and guideways, and so forth."(6) Numbers on imbedded energy appear to be unavailable, complicating comparisons of modes on the basis of energy consumption. Notwithstanding that complication, some could conclude that the numbers in table 1 are helpful, although perhaps not conclusive, in determining whether Amtrak is a cost-effective way to reduce fuel consumption in the United States.(7)


The numbers in table 1 on energy use per passenger-mile by different transportation modes suggest that Amtrak does not conserve energy compared to intercity bus transportation or auto travel for trips longer than 75 miles, but does conserve energy compared to air transportations Consequently, federal financial assistance to Amtrak might not reduce energy consumption to the extent that people would travel by bus or by auto for trips longer than 75 miles, in the absence of Amtrak.

Federal financial assistance to Amtrak could conserve energy, to the extent that those expenditures result in passengers riding Amtrak rather than flying or taking trips shorter than 75 miles by auto.

The far greater fuel efficiency of intercity buses compared to Amtrak suggests that federal financial assistance to intercity bus service might conserve more energy than Federal financial assistance to Amtrak, even if additional buses caused some increase in congestion.


Sources for table 1: U.S. Department of Energy. Office of Transportation Technologies. Transportation Energy Data Book: Edition 15. Report no. ORNL-6856 (Edition 15 of ORNL-5198), by Stacy C. Davis. Oak Ridge National Laboratory. Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia, 22161. May 1995. Various pagings. Table 2.13 at p. 2-22, for Btu per passenger-mile except for autos used for trips over 75 miles. The 2,625 number was derived from the same source, coupled with two other sources: U.S. Department of Transportation. Office of Highway Information Management. National Personal Transportation Surrey, 1990 NPTS Databook, Volume II. Report no. FHWA-PL-94-OlOB, by Patricia S. Hu and Jennifer Young. Prepared by the Center for Transportation Analysis. Energy Division. Oak Ridge

National Laboratory, Oak Ridge, Tennessee. Prepared for the Office of Highway Information Management. Federal Highway Administration. Washington. November 1993. Various pagings. Table 8.15, at p. 8-24, and table 8.16 at p. 8-26; and U.S. Congress. Office of Technology Assessment. Saving Energy in U.S. Transportation. Report no. OTA-ETI-589. U.S. Govt. Print. Off., Washington. July 1994. 266 p., at pp. 41 and 42.

Derivation of Btu for auto trips over 75 miles: From the sources cited above, the 2,625 Btu per passenger-mile by autos on trips over 75 miles was derived using 3,593 Btu per passenger-mile at a load factor of 1.6 for all auto trips adjusted by a load factor of 2.19 for trips over 75 miles.

The OTA analysis, using 1989 numbers, states that 4,063 Btu per passenger-mile (Btu/p-m) are used during highway or intercity travel with a load factor of 1.5 passengers per auto; for city travel, 4,510 Btu/p-m; for work trips, 6,150 Btu/p-m with a load factor of 1.1; for highway travel, 3,470 Btu/p-m; and "perhaps 2,480" Btu/p-m for "long trips with higher load factors ... assuming 2.1 persons per auto." (See pp. 41-42.) The number of Btu for auto trips over 75 miles in length are lower in the OTA report than in table 1 and the other OTA numbers for auto trips are higher than the similar category in table 1. But, the OTA numbers seem generally consistent with the less specific estimates by type and length of trip contained in the Transportation Energy Data Book used for all auto trips in table 1, and with the 2.19 load factor in the National Personal Transportation Survey.

Sensitivity analysis: If a lower load factor for trips over 75 miles is used than the 2.19 in the Department of Transportation and Department of Energy sources cited above, the computed fuel intensity of autos goes up. For example, if a load factor of 2 is used, the Btu would rise to 2,874 per passenger-mile, thereby shifting the energy intensity of these auto trips to 109% compared to Amtrak. Alternatively, the OTA report, although it used a load factor of 2.1, estimated the usage could be 2,480 Btu, making such trips 94% as fuel intense as Amtrak.


1. Bernard A. Gelb, Larry B. Parker, and Fred J. Sissine made suggestions during the preparation of this report.

2. This report does not address air pollution or potential environmental hazards resulting from energy conservation in intercity passenger transportation because the links among fuel consumption, air pollution, and potential environmental hazards are different for various fuels. Notably, the combustion of gasoline and diesel fuel produce a different variety of air pollutants and potential environmental hazards than the use of coal, oil, and nuclear fuel that generate electricity used by Amtrak along the Northeast Corridor from Washington, DC, to New Haven, CT.

3. The numbers in table 1 are modal averages, taking into account variations in load factors, congested routes, and other variables that would affect the outcome in particular circumstances. Consequently, the numbers in table 1 can be viewed as the result after taking such variations into account.

4. A British thermal unit (Btu) is the heat needed to raise the temperature of a pound of water one degree Fahrenheit.

5. Telephone conversation with an Amtrak representative on December 21, 1995.

6. U.S. Congress. Office of Technology Assessment. Saving Energy in U.S. Transportation. Report no. OTA-ETI-589. Washington, U.S. Govt. Print. Off. July 1994. 266 p., at pp. 41-42. The OTA report discusses Amtrak and a large number of conservation options, but the recommendations in the report do not include existing or expanded travel by Amtrak as an important way to reduce future energy consumption.

7. If Amtrak were to cease operations or severely cut back frequency of service between Washington, DC, and New York City, and if most Amtrak passengers were to shift to auto travel, some added highway and metropolitan congestion could occur, resulting in some additional fuel consumption that is not accounted for in the numbers in table 1. Estimating the possible extent of such increased fuel consumption from increased auto travel would be problematical. Similarly, an increase in congestion could occur if Amtrak passengers were to travel by intercity bus, but the far greater energy efficiency of intercity buses compared to Amtrak suggests that the increased fuel consumption resulting from increased congestion could be more than offset by the higher fuel efficiency of buses. Fuel consumption would likely increase to the extent that Amtrak travelers shifted to air transportation

8. As stated above, conclusions based on table 1 need to be tempered by the recognition that the numbers do not include energy (or costs) imbedded in the infrastructure of each mode of intercity passenger transportation, or energy expended in ancillary activities such as powering stations, repairing roadways and guideways, and so forth.

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