Double-stack rail transport is a form of

intermodal freight transport Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation (e.g., rail, ship, aircraft, and truck), without any handling of the freight itself when changing ...

in which railroad cars carry two layers of

intermodal container An intermodal container, often called a shipping container, or a freight container, (or simply "container") is a large metal crate designed and built for intermodal freight transport, meaning these containers can be used across different Mode ...

s. Invented in the United States in 1984, it is now being used for nearly seventy percent of

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

intermodal shipments. Using double stack technology, a freight train of a given length can carry roughly twice as many containers, sharply reducing transport costs per container. On United States railroads, special well cars are used for double-stack shipment to reduce the needed vertical clearance and to lower the

center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For ...

of a loaded car. In addition, the well car design reduces damage in transit and provides greater cargo security by cradling the lower containers so their doors cannot be opened. A succession of larger container sizes have been introduced to further increase shipping productivity in the United States. Double-stack rail operations are growing in other parts of the world, but are often constrained by clearance and other

infrastructure Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and pri ...

limitations.

History

Southern Pacific Railroad The Southern Pacific (or Espee from the railroad initials) was an American Railroad classes#Class I, Class I Rail transport, railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was oper ...

(SP), and Robert Ingram, of SeaLand, debuted the double-stack intermodal car in 1977. SP and Ingram jointly designed the first car with ACF Industries in 1976. At first it was slow to become an industry standard, then in 1984 American President Lines, started working with the

Union Pacific Railroad The Union Pacific Railroad is a Railroad classes, Class I freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United Stat ...

and that same year, the first all double-stack train left

Los Angeles, California Los Angeles, often referred to by its initials L.A., is the List of municipalities in California, most populous city in the U.S. state of California, and the commercial, Financial District, Los Angeles, financial, and Culture of Los Angeles, ...

for South Kearny, New Jersey, under the name of "Stacktrain" rail service. Along the way the train transferred from the UP to the

Chicago and North Western Railway The Chicago and North Western was a Railroad classes#Class I, Class I railroad in the Midwestern United States. It was also known as the "North Western". The railroad operated more than of track at the turn of the 20th century, and over of t ...

and then to

Conrail Conrail , formally the Consolidated Rail Corporation, was the primary Class I railroad in the Northeastern United States between 1976 and 1999. The trade name Conrail is a portmanteau based on the company's legal name. It continues to do busine ...

Sizes and clearances

Double-stack cars come in a number of sizes, related to the standard sizes of the containers they are designed to carry. Well lengths of , and are most common. Heights range from to ("high cube"). Double stack requires a higher clearance above the tracks, or

structure gauge A structure gauge, also called the minimum structure outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of s ...

, than do other forms of rail freight. Double-stack cars are most common in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

where intermodal traffic is heavy and

electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. In the context of history of technology and economic development, electrification refe ...

is less widespread; thus overhead clearances are typically more manageable. Nonetheless, North American railroads have invested large sums to raise bridges and tunnel clearances along their routes and remove other obstacles to allow greater use of double stack trains and to give them more direct routes. Outside North America some rail routes have been built or upgraded to such standards as to allow both electrification with

overhead wire An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, electric multiple units, trolleybuses or trams. The generic term used by the International Union of Railways for the te ...

s and double stacking.

CSX CSX Transportation , known colloquially as simply CSX, is a Railroad classes, Class I freight railroad company operating in the Eastern United States and the Canadian provinces of Ontario and Quebec. Operating about 21,000 route miles () of trac ...

lists three clearance heights above top of rail for double stack service: *Doublestack 1 — *Doublestack 2 — *Doublestack 3 — *Doublestack 4 — The last 2 clearances offer the most flexibility, allowing two high cube containers to be stacked.

Stacking containers

Forty-foot containers are the standard unit length and load bearing points are at the ends of such containers. Longer containers, such as 45, 48 and 53 feet long, still have the load bearing points 40 feet apart, with the excess protruding equally outside this length. Therefore, 40-foot containers, or larger, can be stacked on 20-foot containers if there are two 20-foot containers in a row; however, 20-foot containers cannot be stacked on top of 40-foot or longer containers. The possible double-stacking patterns are: * Two 20 ft in lower and one 40 ft (or longer) in upper stack (allowed in India, China, US) * One 40 ft in lower and another 40 ft (or longer) in upper stack (allowed in India, US) * Two 20 ft in lower and another set of two 20 ft in upper stack. The container coupling holes are all female and double male

twistlock A twistlock or twist lock, together with matching corner castings, as defined in norms including ISO 1161:1984, form a standardized (rotating) connector system, for connecting and securing intermodal, and predominantly ISO-standard internatio ...

s are required to securely mate container stacks together.

Dwarf containers

China had started to experiment using reduced-size containers to be stacked on to normal containers to allow transport under 25 kV overhead line electrification. India has started to build a series of ''dwarf container'' for domestic transport to be run under 25 kV electrification. With a height of they are 662 mm shorter than ISO shipping containers but 162 mm wider while still allowing for 67% more capacity when double stacked as compared to single stack ISO container. The width is comparable to that of North American 53-foot containers.

Weights

Containers have weight limits designed to allow their transport by road

truck A truck or lorry is a motor vehicle designed to transport freight, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construct ...

s, which have lower weight limits than trains. Outside the U.S., a common limit for railways is train length and per

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

. A four axle container car can take . Since a container is limited to , even including the empty weight of the rail car, single stacking uses only part of the load capacity of the railway. A container is limited to and two such can fit into a car for a container, or even three if double-stacking, but not four unless very high axle load is permitted. The North American railways permit two containers as shown in the images on this page. Another consideration is the maximum weight of a train. A maximum length train in Europe, long can have 50 container cars with a total weight of , and more if 20 ft containers are included. This is not far from the limit using standard European (freight) couplers.

Operations

North America

Intermodal containers shipped by rail within North America are primarily long, with

trailer-on-flat-car Trailer on flatcar, also known as TOFC or piggyback, is the practice of carrying semi-trailers on railroad flatcars. TOFC allows for shippers to move truckloads long distances more cheaply than can be done by having each trailer towed by a truck, ...

(TOFC) units used as well. The 53-foot length reflects a common maximum length for highway

semi-trailers A semi-trailer is a trailer (vehicle), trailer without a front axle. The combination of a semi-trailer and a tractor truck is called a ''semi-trailer truck'' (also known simply as a "semi-trailer", "tractor trailer", or "semi" in the United Sta ...

, which varies by state. Major domestic intermodal carriers include: * J. B. Hunt *

Swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIF ...

* Schneider National * Hub Group Containers shipped between North America and other continents consist of mostly and some and containers. Container ships only take 40's, 20's and also 45's above deck. 90% of the containers that these ships carry are 40-footers and 90% of the world's freight moves on container ships; so 81% of the world's freight moves by 40-foot containers. Most of these 40-foot containers are owned by non-U.S. companies like

Maersk (), usually known simply as Maersk ( ), is a Danish Freight transport, shipping and logistics company founded in 1904 by Arnold Peter Møller and his father Peter Mærsk Møller. Maersk's business activities include Port operator, port operat ...

, MSC, and CMA CGM. The only U.S. 40-foot container companies are leasing companies like Textainer, Triton International, and CAI Leasing. Low bridges and narrow tunnels in various locations prevent the operation of double-stack trains until costly upgrades are made. Some

Class I railroad Railroad classes are the system by which Rail freight transport, freight railroads are designated in the United States. Railroads are assigned to Class I, II or III according to annual revenue criteria originally set by the Surface Transportatio ...

companies in the U.S., often in partnership with government agencies, have implemented improvement programs to remove obstructions to double-stack trains. Double-stack projects include: * Heartland Corridor (

Norfolk Southern Railway The Norfolk Southern Railway is a Class I freight railroad operating in the Eastern United States. Headquartered in Atlanta, the company was formed in 1982 with the merger of the Norfolk and Western Railway and Southern Railway. The comp ...

) — $320 million * Norfolk Southern Crescent Corridor — $2.5 billion (estimate) * National Gateway (

CSX Transportation CSX Transportation , known colloquially as simply CSX, is a Class I freight railroad company operating in the Eastern United States and the Canadian provinces of Ontario and Quebec. Operating about 21,000 route miles () of track, it is the lead ...

) — $700 million * Commonwealth Railway — $69 million * Chicago Region Environmental and Transportation Efficiency Program — $3 billion (estimate) * Cross-Harbor Rail Tunnel proposed to connect rail freight lines in

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

with

Long Island, New York Long Island is a densely populated continental island in southeastern New York (state), New York state, extending into the Atlantic Ocean. It constitutes a significant share of the New York metropolitan area in both population and land are ...

. — $10–14 billion (estimate) * Continental Rail Gateway (

Canadian Pacific Railway The Canadian Pacific Railway () , also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canadian Pacific Kansas City, Canadian Pacific Ka ...

), proposed tunnel between

Detroit Detroit ( , ) is the List of municipalities in Michigan, most populous city in the U.S. state of Michigan. It is situated on the bank of the Detroit River across from Windsor, Ontario. It had a population of 639,111 at the 2020 United State ...

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

and Windsor,

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

to replace the existing

Michigan Central Railway Tunnel The Michigan Central Railway Tunnel is a railroad tunnel under the Detroit River connecting Detroit, Michigan, in the United States with Windsor, Ontario, in Canada. The U.S. entrance is south of Porter and Vermont streets near Rosa Parks Bouleva ...

. — $400 million File:DTTX 724681 20050529 IL Rochelle.jpg, Part of a double-stack train, with 53-foot containers File:APM Terminals WJ Grimes.JPG, Double-stack train loaded at APM Terminals in

Portsmouth, Virginia Portsmouth is an Independent city (United States), independent city in southeastern Virginia, United States. It lies across the Elizabeth River (Virginia), Elizabeth River from Norfolk, Virginia, Norfolk. As of the 2020 United States census, 2020 ...

File:Intermodal shipping containers on a railway flat car.jpg, Transportación marítima mexicana (TMM)

containers A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping. Things kept inside of a container are protected on several sides by being inside of its structure. The term ...

on a double stack train car, 2008 File:Cajon Intermodal.jpg, A

BNSF BNSF Railway is the largest freight railroad in the United States. One of six North American Class I railroads, BNSF has 36,000 employees, of track in 28 states, and over 8,000 locomotives. It has three transcontinental routes that provide ...

double-stack train passing through

Cajon Pass Cajon Pass (; Spanish: ''Puerto del Cajón'' or ''Paso del Cajón'') is a mountain pass between the San Bernardino Mountains to the east and the San Gabriel Mountains to the west in Southern California. Created by the movements of the San Andr ...

in California, with a mix of 20-foot and 40-foot containers

Outside North America

On the vast majority of its network, Europe has more restricted

loading gauge A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and k ...

and train weight limits as well as

axle load The axle load of a wheeled vehicle is the total weight bearing on the roadway for all wheels connected to a given axle. Axle load is an important design consideration in the engineering of roadways and railways, as both are designed to tolerate a m ...

limits. In other words, many bridges and tunnels are too low for double-stacking. In addition, since European electrification standards generally predated double stacking and were not designed to accommodate for larger clearances than those permitted by existing bridges and tunnels, the overhead catenary in Europe is also too low to accommodate double stacking. Only a few newly built routes make accommodation for possible double stacking in the future such as the

Betuweroute The Betuweroute is a double track Freight rail transport, freight railway between Rotterdam and Germany. is the official name, after the Betuwe area through which the route passes. The line is popularly called Betuwelijn, after an older local ...

in the Netherlands which however links to no other railway line allowing double stacking. Standard gauge railways in North America and China must use special well cars to lower the

, fit within the

and in China allow double stack trains to run under specially heightened

overhead lines An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, Electric multiple unit, electric multiple units, trolleybuses or trams. The generic term used by the International Union ...

broad gauge A broad-gauge railway is a railway with a track gauge (the distance between the rails) broader than the used by standard-gauge railways. Broad gauge of , more known as Russian gauge, is the dominant track gauge in former Soviet Union countries ...

used in India enables trains to carry standard shipping containers double-stacked on standard flat wagons. Flat wagons, in addition to being much less expensive than well wagons, can carry more containers in a given length of train. Indian Railways is able to carry containers double-stacked on standard flat wagons at . Experiments with triple-stacked operation using lower, containers, were done unsuccessfully in 2006. Experiments in India for double stacking using flatcars under

25 kV AC Railway electrification systems using alternating current (AC) at are used worldwide, especially for high-speed rail. It is usually supplied at the standard utility frequency (typically 50 or 60Hz), which simplifies traction substations. The dev ...

overhead line An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, Electric multiple unit, electric multiple units, trolleybuses or trams. The generic term used by the International Union ...

s set above rail have begun with funds given by Japan. *

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

- double-stacked trains operate between

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

Adelaide Adelaide ( , ; ) is the list of Australian capital cities, capital and most populous city of South Australia, as well as the list of cities in Australia by population, fifth-most populous city in Australia. The name "Adelaide" may refer to ei ...

, Darwin and

Parkes, New South Wales Parkes is a town in the Central West (New South Wales), Central West region of New South Wales, Australia. It is the main settlement in the local government in Australia, local government area of Parkes Shire. Parkes had a population of 9,83 ...

clearances. , the Inland Railway between Melbourne and Brisbane was being built for operation of double stacked trains. *

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

- Double Stacked trains in Brazil already operates between the intermodal terminal of Sumaré-SP and Rondonópolis-MT (around 1000 km). The operation started in June 2019 by Brado Logística. Besides that, a brand new railroad called "Ferrovia Norte - Sul" will also operate with Double Stack container trains. The operation will start in 2021. *

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

- A number of select Class I trunk railway lines in China were constructed or upgraded with

high enough to operate double-stacked container trains but currently do not see any double-stack service, such as the Nanjing–Qidong railway, Nantong–Shanghai railway, Guangzhou–Zhuhai railway and sections of the Beijing–Kowloon railway and Longhai railway. Since 2018,

China Railway China State Railway Group Co., Ltd., doing business as China Railway (CR), is the national passenger and freight railroad corporation of the China, People's Republic of China. China Railway operates passenger and freight Rail transport in Chi ...

started operating double-stacked standard containers in well-wagons hauled by

electric locomotive An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a Battery (electricity), battery or a supercapacitor. Locomotives with on-board fuelled prime mover (locomotive), ...

s under overhead lines from

Port of Ningbo-Zhoushan The Port of Ningbo-Zhoushan is List of busiest ports by cargo tonnage, the busiest port in the world in terms of cargo tonnage. It handled 888.96 million tons of cargo in 2015. The port is located in Ningbo and Zhoushan, on the coast of the East ...

along the Xiaoshan–Ningbo railway and Chuanshan Port branch line to

Shaoxing Shaoxing is a prefecture-level city on the southern shore of Hangzhou Bay in northeastern Zhejiang province, China. Located on the south bank of the Qiantang River estuary, it borders Ningbo to the east, Taizhou, Zhejiang, Taizhou to the south ...

. Another railway in the area capable of operating double stack containers under

, the Ningbo–Jinhua railway connecting

to Yiwu and

Jinhua Jinhua is a prefecture-level city in central Zhejiang province in eastern China. It borders the provincial capital of Hangzhou to the northwest, Quzhou to the southwest, Lishui to the south, Taizhou, Zhejiang, Taizhou to the east, and Shaoxin ...

, is under construction. Other under construction railways capable of operating double stack containers under

are the Liuzhou-Guangzhou Railway between

Guangdong ) means "wide" or "vast", and has been associated with the region since the creation of Guang Prefecture in AD 226. The name "''Guang''" ultimately came from Guangxin ( zh, labels=no, first=t, t= , s=广信), an outpost established in Han dynasty ...

and

Guangxi Guangxi,; officially the Guangxi Zhuang Autonomous Region, is an Autonomous regions of China, autonomous region of the China, People's Republic of China, located in South China and bordering Vietnam (Hà Giang Province, Hà Giang, Cao Bằn ...

, Lanzhou-Chongqing Railway and a line from

Guiyang Guiyang; Mandarin pronunciation: ; Chinese postal romanization, alternatively as Kweiyang is the capital of Guizhou, Guizhou province in China. It is centrally located within the province, on the Yunnan–Guizhou Plateau, eastern part of the Yun ...

via

Nanning Nanning; is the capital of the Guangxi, Guangxi Zhuang Autonomous Region in South China, southern China. It is known as the "Green City (绿城) " because of its abundance of lush subtropical foliage. Located in the South of Guangxi, Nanning ...

to the port city of Qinzhou. China's National Transportation Outline envisions a network of electric double stack container services connecting all major cities and ports. *

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

Mundra Port Mundra Port is India's first private port, largest Containerization, container List of ports in India, port in India and largest commercial port, located on the northern shores of the Gulf of Kutch near Mundra, Kutch district, Gujarat. Formerly ...

and Pipavav Port operate double-stacked diesel and electric trains on gauge using flat wagons. It is one of only three countries to commercially double stack tall (high cube) containers on a train. India is building the Dedicated Freight Corridor an electric traction freight railway network which can transport double-stack international standard containers. The tracks are entirely grade-separated and have a generous

of width and maximum height allowing for the double-stacked

shipping container A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated box design, corrugated b ...

on flatcars to be transported, in contrast to wellcars used in other countries for double-stack rail transport. This allows for single trains to have a 400-container capacity. *

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

- The Mombasa-Nairobi standard gauge railway has been built for the operation of double-stacked trains, the first such trains being launched on October 1, 2018. All future extensions will be built to similar standards. *

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

- The

, a freight rail line between Rotterdam and the German border built in 2007 is prepared for double-stacking insofar as tunnels and bridges have been built to accommodate double stack trains to reduce the cost and time of any future upgrade to the network. The current catenary wire is too low for double stack rail transport (meaning the catenary would have to be raised to allow double stacking) and the upgrade is dependent on the German section of the railway connection as there are no accommodations for future double stack transport on any line connecting to the Betuweroute on the German side. *

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

- The rebuilt Panama Canal Railway operates double-stack container trains 47.6 miles (76.6 km) across the

Isthmus of Panama The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America, North and South America. The country of Panama is located on the i ...

from Colón on the Atlantic Ocean, to Balboa on the Pacific, near

Panama City Panama City, also known as Panama, is the capital and largest city of Panama. It has a total population of 1,086,990, with over 2,100,000 in its metropolitan area. The city is located at the Pacific Ocean, Pacific entrance of the Panama Canal, i ...

. *

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the centre of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about , making it the List of Asian countries ...

- Saudi Railways Organization line to

Dammam Dammam (Arabic: الدمام ad-Dammām) is a city and governorate, and the capital of the Eastern Province of Saudi Arabia. Located on the coast of the Persian Gulf, it had a population of 1,386,166 as of 2022, making it the country's fifth- ...

References

External links

CAI leasing

CAI Goods in motion
{{Intermodal containers Freight rolling stock Intermodal containers