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- Title: Public Roads – Tube Freight Transportation
- Author: Lawrence Vance and Milton K. Mills, US Federal Highway Administration
- Source: http://www.tfhrc.gov/pubrds/fall94/p94au21.htm
Text is based on ‘Tube Transportation’, Feb 1994, John A Volpe National
Transportation Systems Centre, RSPA/VNTSC-SS-HW495-01.
- Copyright: US Federal Highway Administration
- Date: 1994
Under a research program on advanced freight movement, the Federal Highway
Administration (FHWA) with the support of the John A. Volpe National
Transportation Systems Center is examining the technical and economic
feasibility of tube transportation systems to address future freight
Tube freight transportation is a class of unmanned transportation systems in
which close-fitting capsules or trains of capsules carry freight through tubes
between terminals. All historic systems were pneumatically powered and often
referred to as pneumatic capsule pipelines. One modern proposed system called
SUBTRANS uses capsules that are electrically powered with linear induction
motors and run on steel rails in a tube about two meters (6½ feet) in diameter.
The system can be thought of as a small unmanned train in a tube carrying
An underground tube transportation system can carry high-volume freight into
highly congested areas with minimum effect on surface transportation systems. If
this system were implemented in congested areas, passenger vehicles could be
separated from freight vehicles with improvements in efficiency and safety for
both modes. The improvement in efficiency would result in lower freight rates
and a lower environmental impact on air quality and noise. Also, the Texas
Transportation Institute at Texas A&M estimates that productivity lost to
traffic congestion costs more than $40 billion per year.
The separation of trucks and automobiles was recommended by the Hoover
Commission on Highway Safety in the late 1920s. The concept has been reevaluated
periodically. It is now timely to initiate a reevaluation. Such an analysis
should be based on current and future highway needs in the framework of the
emerging economic and market environment anticipated in the early 21st century.
However, it must be stressed that tube freight transportation is a promising
concept for a future system. A great deal of additional research and development
and the commitment of substantial resources are necessary to produce even a
prototypical operational system. The initial operational systems are most likely
in major metropolitan areas where current and projected traffic congestion
inhibits increased movement of freight by trucks; a nationwide tube freight
transportation network will not be feasible for many years, if at all. While
tube freight systems have considerable potential to move goods efficiently and
offer significant advantages, such systems are not likely to have any near-term
impact on the trucking or railroad industries.
This article will discuss the history and advantages of tube freight systems,
current tube freight system proposals, and issues relative to implementing such
a freight system.
Tube Transportation History
Tube transportation has a history that extends back at least 200 years. During
this period, systems for both passengers and freight have been built and
operated. Some are in operation today. In addition, there have been many more
proposals that were never built. All of the historical tube transportation
systems were pneumatically powered.
George Medhurst, a London businessman, is considered the earliest proponent of
pneumatic-powered railways although there were a few earlier, brief suggestions
from others. He first published a freight proposal in 1810, a passenger proposal
in 1812, and a more comprehensive set of proposals in 1827.
Despite four demonstration systems, including a 95-m (312-ft), underground
system built in New York City in 1869-70, no large-size tube transportation
system has been introduced into common carrier service. The primary result of
this activity was to lend support to the development of underground electric
railway systems for urban passenger transportation. However, small diameter
pneumatic pipelines have been providing reliable freight transportation around
the world for more than 150 years.
Common applications of pneumatic pipelines before World War II were the high-
priority movement of documents and parts in industrial environments and movement
of letters and telegrams under city streets to bypass congestion. These systems
were built with tubes ranging from 5 to 20 centimeters (2 to 8 inches) in
diameter. Such systems are still being built today to expedite small shipments.
After World War II, larger pneumatic systems were developed and built in Japan
and Russia to move bulk materials such as limestone and garbage. These systems
had considerably greater throughput as a result of both their increased
diameters of 0.9 to 1.2 m (3 to 4 ft) and their mode of operation, which allowed
more capsules to move through the tube at one time. By the early 1970s, several
groups began to give consideration to the use of these pipeline designs for
common carrier, general merchandise freight applications using tubes 1.2 to 1.8
m (4 to 6 ft) in diameter.
Future Freight Growth
By 2015, surface transportation is expected to grow well beyond current traffic
levels with significant constraints on construction of new highways due to
economic and environmental considerations. Figure 1 shows truck traffic growth
from 1960 through 1990 with projected traffic through 2020. (1) By the year
2020, intercity trucking is projected to increase by more than 50 percent over
1990 levels. Since new transportation routes are expected to be difficult to
obtain, major emphasis is presently being placed on intelligent vehicle-highway
systems (IVHS) that will more efficiently use the present highway system. Use of
subsurface tube freight transportation in highly congested areas would allow
IVHS type systems to operate more efficiently by removing some truck traffic
Figure 1: Truck freight growth, 1960-2020. (upward) Not Cached.
Potential Advantages of Tube Freight Transportation Systems
Tube transportation systems have a number of attractive features that make them
worthy of evaluation as alternatives for future freight transportation systems.
Because such systems are unmanned and fully automatic, they are safer than truck
or railroad systems. When traveling down grades, the capsules may be able to
regenerate energy for improved energy efficiency. Because they are enclosed,
they are unaffected by weather and are not subject to most common rail and
highway accidents. Hazardous cargo can be more safely transported than on
surface systems. The tubes could also be used as conduits for communication
cables for the future information highway. Benefits from reducing the number of
trucks carrying freight in congested areas by tube freight transportation
- Reduced traffic congestion.
- Reduced traffic accidents, injuries, and fatalities.
- Reduced traffic exhaust pollution and traffic noise.
- Reduced damage to roadways and bridges.
- Reduced petroleum fuel consumption.
- Increased control over delivery schedules.
- Lower freight transportation costs.
The tubes can be placed above, on, or below ground. Underground locations are
useful in environmentally sensitive areas and are important where surface
congestion makes surface right-of-way difficult or expensive to obtain. Much
right-of-way potentially exists below our present highway system. However, there
are potential environmental impacts of construction, especially if cut and cover
construction is used.
Current Tube Freight Transportation Proposals
The SUBTRANS concept is to provide long-haul freight transportation in capsules
running in a tube about two m (6½ ft) in diameter (see figures 2 and 3). (2) The
capsules would be propelled by linear induction motors. Non-pneumatic propulsion
of the system is the subject of a U.S. patent granted to William Vandersteel of
North Bergen, N.J., in 1984 (patent number 4458602). The system would be totally
automated and is intended to operate at a constant speed of about 100 kilometers
per hour (60 miles/h). Capsules are expected to be switched from the main routes
to terminals or other routes at speed using electromagnetic switching
techniques. The capsules are unconnected; pneumatic pressure provides buffering
between capsules because of the small clearance between the capsule and the
tube. The SUBTRANS capsules are designed to accept pallets to facilitate rapid
loading and offloading. Automated warehousing is an option in this concept with
the capsules being used for temporary warehouse storage. The developer claims a
maximum throughput of 1875 capsules per hour, which is roughly 16,500 metric
tons/h (18,200 short tons/h)(1) at average cargo densities. At this time,
SUBTRANS is an undeveloped concept.
Professor Masaki Koshi of the University of Tokyo has proposed an underground
freight transportation system for the city of Tokyo. (3) This system uses
standard subway clearances between the capsules and the tube; therefore, the
capsules do not develop pneumatic pressure between themselves. The purpose of
this automated freight system is to significantly reduce truck traffic. This
system, which proposes to use linear induction traction, is currently being
evaluated and developed by the Ministry of Construction. Non-standard containers
are designed to be moved through 5.5-m- (18-ft-) diameter tubes. Automated
loading and unloading of the containers at terminals is part of this concept. A
300-km- (186-mi-) network is projected with automated terminals that move the
containers to the first basement of major shippers/receivers or to street level
for local distribution to small consignees. An experimental line a few
kilometers long is expected to be initiated soon.
Previous Tube Freight Transportation Proposals
A proposal similar to SUBTRANS was made by the British Hydro-mechanics Research
Association (BHRA) in the early 1970s for a British national tube transportation
system for general commodity freight. The British system proposed 11-metric ton
(12.1-short ton) capsules operating in a 1.5-m- (5-ft-) diameter tube. (4)
Speeds of 30 to 50 km/h (20 to 30 mi/h) were anticipated at a rate of 100 to 150
capsules per hour. Pneumatic pressures for propulsion are generated by jet pumps
developed and patented by BHRA. Although the British are no longer actively
promoting this technology, we assume they, as well as others who are still
active in the field, remain interested in general cargo applications.
Current Tube Freight and Passenger Transportation Proposals
The Swiss high-speed, magnetic levitation (maglev) proposal would use a 4.5-m-
(15-ft-) diameter tube. (5,6) The tube would be buried 40 m (130 ft) deep in
most areas, deeper under mountains. Speeds in the range of 250 to 300 km/h (124
to 186 mi/h) are projected. Linear induction motors are to be used. The purpose
of the tube transportation approach is to reduce tunneling costs by reducing the
tunnel diameter. Air resistance is reduced through evacuation of the tunnel. The
alternative would be to use a very large cross-section bore to minimize
aerodynamic drag and undesirable pressure changes at tunnel entrances and exits.
This proposed system is currently under serious evaluation by the Swiss
government. The primary motivation for this system is to obtain the benefits of
a high-speed passenger system in a region where there are major environmental
constraints and new right-of-way is unavailable.
The National Aeronautics and Space Administration “New Millennium Transportation
System” proposes two national maglev systems. (7) The first, a surface system,
is not a tube system. The second, a “hypervelocity” system, would be an
underground system operating in evacuated tunnels at speeds up to 6,400 km/h
Operational Pneumatic Tube Transportation Systems for Bulk Materials
Nippon Steel Corporation and Daifuku Machinery Works Ltd., using an early
license from TRANSCO of Houston, Texas, have built a 0.6-m- (2-ft-) diameter,
1.5-km (0.9-mi), double line to move burnt lime in Nippon Steel’s Muroran Number
2 steel plant. (8) This elevated line was built in the mid-1980s and
uses capsule trains (two cars per train) to move 22,000 metric tons (24,266
short tons) per month. This system is called AIRAPID.
Sumitomo Cement Co. built a similar system in 1983 to move limestone 3.2 km (2
mi) between a mine and their cement plant. (9) The 1-m- (3.2-ft-) diameter pipe
carries three car capsule trains delivering 2.2 million metric tons (2.43
million short tons) per year. This system was originally based on a Russian
license but was considerably redesigned by the company.
A number of tube systems, called TRANSPROGRESS systems, for moving crushed rock
are being used in the former Soviet Union. (10) An 11-km (6.8-mi) line for
garbage was built in 1983 from St. Petersburg to an outlying processing facility
using TRANSPROGRESS technology. This technology has also been applied to
Technical Feasibility and System Considerations
Tube transportation systems for common carriage exist primarily as concepts at
this time. Encapsulated freight may be conveyed through air tubes propelled by
differential (pneumatic) pressure acting on the opposite faces of capsules
closely fitted in the tubes. Other systems of propulsion could include
conventional electric motors, linear induction motors, or mechanical/cable
Pneumatically powered systems are clearly feasible because they have been built
and operated in the past, although not in general merchandise service. Linear
induction motor powered systems are also technically feasible although such
systems have not been demonstrated or, in fact, designed in detail yet. These
systems are not off-the-shelf; they will require specific designs for specific
applications. The design features for a number of necessary elements are
All capsule systems will require power distribution systems and facilities for
inspection and monitoring, maintenance, and control and communication. The
simplicity in the design and operation of the capsule will bear directly on the
costs associated with these requirements.
Simplicity of the design and operation, coupled with a simple capsule
configuration promising relatively easy and inexpensive fabrication and
operation, is the advantage claimed for linear induction propulsion.
It is in the area of automatic control that tube transportation would seen to
have advantages over competing modes of freight shipment. With a dedicated,
weather-proof, intrusion-proof capsule and guideway system, automatic controls
available today could provide almost complete automation from point-of-freight
origin to destination. Given the state of the art and development of existing
control systems for passenger transportation, where safety and operational
standards are much higher than they would be for freight, it can be assumed that
automatic controls would be somewhat readily available and adaptable. This would
apply regardless of the electric and/or pneumatic elements of the propulsion
It is assumed that substantial portions of any tube transportation system will
be constructed underground, especially in urban areas. Because tunneling costs
are so high, many tube system proponents scale their concepts down in size. But
even with scaled down tubes of about 1.8 m (6 ft) inside diameter, these systems
have more potential throughput capacity than railroads. And it is in the major
urban areas that underground tube systems are most promising and most needed to
reduce traffic congestion and air pollution caused by trucks.
There are numerous design and construction issues to be resolved — for example,
size of the tube, configuration of the system (separate tubes for each direction
or a looped line, direct system access for customers, intermodal transfer
capabilities, short-term storage capacity), capability to move refrigerated
freight, appropriate venting of tunnels, and switching. Switching, the transfer
of capsules at speed from one line to another, remains somewhat problematic in
tube transportation systems. Current monorail and maglev switch mechanisms are
large and cumbersome and cannot handle speeds up to 100 km/h (60 mi/h) during
Economics of Tube Freight Transportation Systems
Tube transportation systems are inherently high capital cost, low operating cost
systems, but the economic feasibility of tube transportation systems carrying
general merchandise is unknown as no such system has been built and operated in
A study of the economics of tube transportation that was sponsored by the U.S.
Department of Transportation in the late 1970s indicates tube transportation may
be competitive with long-haul truck and railroad operations. (11,12) This study
by the University of Pennsylvania was performed without detailed tube designs
and associated cost data. Such data for currently proposed concepts is also
lacking as previously noted.
As a result, engineering development studies and concept demonstrations are
needed to provide refined estimates of the system economics. Cost estimates need
to be made for specific routes because a major part of the capital requirement
is tunneling costs, which are highly variable and site specific. Port or urban
core access corridor lines, where high land values and surface congestion would
enhance the value of tube transportation, would appear likely study candidates.
Package delivery firms, less-than-truckload trucking firms, and the U.S. Postal
Service are potential users of such a system.
A national tube transportation network would clearly be in competition with both
motor carriers and railroads; however, development of a nationwide system is
Fully automated tube freight transportation systems have the potential to
provide reliable, predictable, rapid, safe, and secure service. Because each
capsule can be dispatched when loading is completed, there is no delay while
sufficient cars are loaded and assembled into a train as in standard railroad
practice. Since the system is very predictable in operation, complete and real-
time information on the location of each capsule can be maintained very
inexpensively. These attributes result in a high level of service and should be
particularly attractive to just-in-time manufacturers.
A major benefit of tube transportation is safety. Tube freight systems, since
they are automated, without onboard personnel, and operate in isolation, are
likely to be far safer than trucks in congested areas with mixed traffic.
Currently, several national organizations are lobbying for a reduction in heavy
truck traffic. Tube transportation is also safer than railroads since its design
will eliminate highway crossings and unauthorized intruder accidents. Highway
accidents involving heavy vehicles result in about 4,000 fatalities per year in
the United States, and railroad accidents cause about 1,000 fatalities each
In addition, pneumatic pipeline freight systems, the antecedents of current tube
transportation proposals, have had high operational reliability virtually free
of accidents and with an extremely low rate of cargo damage. Tube transportation
systems offer clear environmental and energy-saving benefits, particularly in
comparison with trucks. All current tube transportation proposals envision the
use of electrical power, and they are likely to be very clean and energy-
efficient. Air pollution from trucks will be reduced in proportion to the number
of trucks removed from the road. Underground systems reduce intrusion in
environmentally sensitive areas, and they are especially beneficial where
surface land values are high, where surface conditions are already congested, or
surface routes are unavailable. These are not new issues, but they are becoming
more important with nationwide urban growth. (13) Tube transportation has no
significant energy advantage over railroads, but if trucks were removed from the
congested areas, highway fuel use would be reduced.
Historically, there is a precedent for underground freight operations. The most
notable underground freight system was the 80-km (50-mi) electric railway system
built under the city of Chicago for the collection and distribution of general
cargo and coal. The Chicago system operated from 1904 to 1958, interfacing with
the main-line railroads. The Tokyo tube transportation proposal previously
mentioned would perform the same function as the Chicago system, except that the
system in Tokyo would be automated and would interface primarily with trucks.
Any tube freight system operating as a common carrier will be required to
transfer freight to other carriers for final delivery, except to large
consignees with private, direct access (like railroad sidings). In most cases,
trucks are the most likely off-line carrier. Currently, intermodal transfers
between trucks, railroads, and ships are facilitated by the use of standard
intermodal containers. (14) In addition, truck trailers act as containers when
they are hauled on railroad flat cars. Intermodal shipments are increasing. To
be successful, any tube freight system must have some means of efficient
intermodal transfer, such as standard containers. However, to handle the current
standard intermodal containers, tube diameters of about 3 to 3.66 m (10 to 12
ft) are necessary, and such tubes would require about four times the capital
cost of the 1.8-m- (6-ft-) diameter tubes advocated by most promoters and, thus,
would be much less economically attractive.
Approaches to Introduce Tube Freight
It is evident that a comprehensive tube freight system cannot be financially and
physically implemented overnight even if this were a national objective. Several
transitional approaches can be envisioned.
The first option is to build the most needed and financially viable segments in
congested areas. This approach has the obvious disadvantage of requiring
standardization after initial segments are built and operating.
A second approach is to develop a national plan with appropriate standards
established in advance. This was the general approach taken to implement the
interstate highway system. This approach would appear more appropriate for the
introduction of tube freight transportation in congested areas. However, it has
the disadvantage of requiring an extensive period of planning, consensus-
building, and enactment.
A third approach is to assume tube freight transportation would only provide
niche, general commodity services and allow totally private planning and
development with limited enabling legislation and, perhaps, access to federal
Future Tube Freight Transportation Plans
A panel of transportation experts – representing truck and rail companies,
freight users, state and local governments, construction companies, and others
– will review the current status of tube freight transportation and develop a
recommended federal position concerning future research and development of such
systems. Two research tasks will provide estimates of future tunneling costs,
tunnel liners, capsules, linear induction motors, and associated systems. In
addition, estimates of future freight capacity requirements, particularly in
congested areas, will be determined.
Likely increases in freight traffic beyond the year 2000, combined with
increasing restrictions on the expansion of surface facilities, has led FHWA to
examine some alternatives for use in congested areas. Tube transportation is one
alternative that is gaining worldwide attention. Use of existing highway rights-
of-way is an attractive feature of tube transportation. There are a number of
other desirable features and advantages relating to productivity, safety,
environmental issues, and energy savings. Because of the potential of such
systems, FHWA is currently studying estimated costs of tube transportation
systems, particularly liner induction motor-powered approaches, as a first step
in the process of examining their economic viability. A necessary part of cost
estimation is development of conceptual designs, which could lead to functional
(1) National Transportation Statistics, Annual Report, Historical Compendium
1960-1992 (with linear projection to 2020), Bureau of Transportation Statistics,
U.S. Department of Transportation, September 1993.
(2) William Vandersteel. The Future of Our Transportation Infrastructure,
Ampower Corporation, North Bergen, N.J., 1993.
(3) Masaki Koshi. “An Automated Underground Tube Network for Urban Goods
Transport,” Journal of International Association of Traffic and Safety Sciences,
Vol. 16, No. 2, 1992.
(4) R. Livesey. “Blown Freight Is a Lovely Change From Road and Rail,” The
Engineer, London, England, Oct. 28, 1971.
(5) “Im Nächsten Jahrtausend in 57 Minuten von Genf nach Zürich,” Der Bund,
Sonderbeilage, Bern, Switzerland, Sep. 8, 1992.
(6) “Vacuum Technology Weighed for Swiss Maglev Proposal,” MAGLEV News, Vol. 1,
No. 15, May 17, 1993.
(7) “New Millennium Seeks Support From NMI Officials,” MAGLEV News, Mar. 22,
(8) “AIRAPID Capsule-Tube Transport System,” promotional brochure of Nippon
Steel Corp., Daifuku Machinery Works Ltd., Chiyoda-Ku, Tokyo, Japan, undated.
(9) “The Capsule Liner,” promotional brochure of Plant Engineer Division of
Sumitomo Metal Ind. Ltd., Chiyoda-Ku, Tokyo, Japan.
(10) “TRANSPROGRESS Systems for Pipeline Pneumatic Container Freight
Transportation,” promotional brochure of Licinsintorg, Moscow, Russia, 1986.
(11) I. Zandi, W.B. Allen, E.K. Morlok, K. Gimm, T. Plaut, and J. Warner.
Transport of Solid Commodities via Freight Pipeline, Department of Civil and
Urban Engineering, University of Pennsylvania, Philadelphia, Pa., published in
five volumes for the Department of Transportation, Publication No. DOT-TST-76T-
35 through DOT-TST-76T-39, July 1976.
(12) I. Zandi, J. Warner, B. Allen, J. Kerrigan, C. Younkin, and K. Thomas.
Transport of Solid Commodities via Freight Pipeline, Department of Civil and
Urban Engineering, University of Pennsylvania, Philadelphia, Pa., published in
two volumes, December 1978.
(13) The Need for a National System of Transportation and Utility Corridors,
U.S. Department of the Interior, Washington, D.C., July 1, 1975.
(14) Eric Rath. Container Systems, John Wiley & Sons Inc., 1973.
Lawrence Vance has worked in the field of new systems studies since he did a
study of new and novel transportation systems for the Bay Area Transportation
Study Commission in 1968-69. At the John A. Volpe National Transportation
Systems Center since 1971, he has performed a number of new systems studies
interspersed with other assignments. He recently spent five years aiding the
U.S. Air Force to automate their transportation information systems. He received
his doctorate in engineering from the Institute of Transportation and Traffic
Engineering (now the Institute of Transportation Studies) of the University of
California at Berkeley in 1970. He also has degrees in mechanical engineering.
Milton K. (Pete) Mills is an electronic engineer in the FHWA’s Office of
Advanced Research. From 1963 to 1966, he tested and evaluated aircraft antenna
systems at the U.S. Naval Air Test Center, Patuxent River, Md. From 1966 to
1968, he designed and patented a number of spacecraft antenna systems at NASA’s
Goddard Space Flight Center in Greenbelt, Md. At the FHWA’s Turner-Fairbank
Highway Research Center in McLean, Va., since 1968, he has managed the
development and evaluation of vehicle sensor systems. He received his bachelor’s
degree in electrical engineering from North Carolina State University and his
master’s degree in electrical engineering from Catholic University in 1975.