Double-stack rail transport

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A container train passing through Jacksonville, Florida, with 53 ft (16.15 m) containers used for shipments within North America Freight train in Jacksonville, FL.jpg
A container train passing through Jacksonville, Florida, with 53 ft (16.15 m) containers used for shipments within North America

Double-stack rail transport is a form of intermodal freight transport in which railroad cars carry two layers of intermodal containers. Invented in the United States in 1984, it is now being used for nearly seventy percent of United States 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 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.

Contents

Double-stack rail operations are growing in other parts of the world, but are often constrained by clearance and other infrastructure limitations.

History

Southern Pacific Railroad (SP), and Robert Ingram, of SeaLand, debuted the double-stack intermodal car in 1977. SP, Robert Ingram jointly designed the first car with ACF Industries in 1976. [1] [2] [3] At first it was slow to become an industry standard, then in 1984 American President Lines, started working with the Union Pacific Railroad and that same year, the first all double-stack train left Los Angeles, California 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 and then to Conrail.

Sizes and clearances

AAR Plate-H loading gauge Gabarit AAR Plate-H.png
AAR Plate-H loading gauge

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 12.19 m (40.0 ft), 14.63 m (48.0 ft) and 16.15 m (53.0 ft) are most common. [5] Heights range from 2.44 m (8 ft 0 in) to 2.908 m (9 ft 6+12 in) ("high cube").

Double stack requires a higher clearance above the tracks, or structure gauge, than do other forms of rail freight. Double-stack cars are most common in North America where intermodal traffic is heavy and electrification 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 wires and double stacking. [6] [7]

CSX lists three clearance heights above top of rail for double stack service: [8]

The last 2 clearances offer the most flexibility, allowing two high cube containers to be stacked.

Stacking containers

Load bearing of container stacking is at the 40-foot coupling Container Stacking.jpg
Load bearing of container stacking is at the 40-foot coupling

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:

The container coupling holes are all female and double male twistlocks are required to securely mate container stacks together.

Dwarf containers

China had started[ when? ] 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[ when? ] to build a series of dwarf container for domestic transport to be run under 25 kV electrification. With a height of 6 feet 4 inches (1,930 mm) 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. [11] [ failed verification ] The width is comparable to that of North American 53-foot containers.

Weights

Containers have weight limits designed to allow their transport by road trucks, which have lower weight limits than trains. Outside the U.S., a common limit for railways is 8 tonnes per metre (8.1  short ton / yd ; 7.2  long ton /yd) train length and 22.5 tonnes (22.1 long tons ; 24.8 short tons ) per axle. A four axle container car can take 90 tonnes (99.2 short tons; 88.6 long tons). Since a container is limited to 30.5 tonnes (33.6 short tons; 30.0 long tons), even including the empty weight of the rail car, single stacking uses only part of the load capacity of the railway. A 20-foot (6.1 m) container is limited to 24 tonnes (26.5 short tons; 23.6 long tons) and two such can fit into a car for a 40-foot (12.2 m) container, or even three if double-stacking[ citation needed ], but not four unless very high axle load is permitted. The North American railways permit two 53-foot (16.15 m) containers as shown in the images on this page.

Another consideration is the maximum weight of a train. A maximum length train in Europe, 750 m (2,461 ft) long can have 50 container cars with a total weight of 2,250 tonnes (2,480 short tons; 2,210 long tons), and more if 20 ft containers are included. This is not far from the limit using standard European (freight) couplers.[ citation needed ]

Operations

North America

Intermodal containers shipped by rail within North America are primarily 53 feet (16.15 m) long, with trailer-on-flat-car (TOFC) units used as well. The 53-foot length reflects a common maximum length for highway semi-trailers, which varies by state. [12] Major domestic intermodal carriers include:

Containers shipped between North America and other continents consist of mostly 40-foot (12.19 m) and some 45-foot (13.72 m) and 20-foot (6.10 m) 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, MSC, and CMA CGM. The only U.S. 40-foot container companies are leasing companies like Textainer, Triton International, [13] and CAI Leasing. [14]

Low bridges and narrow tunnels in various locations prevent the operation of double-stack trains until costly upgrades are made. Some Class I railroad 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:

Outside North America

Double stack train on the Panama Canal Railway Panama Canal Railway - Container Train.JPG
Double stack train on the Panama Canal Railway

On the vast majority of its network, Europe has more restricted loading gauge and train weight limits as well as axle load 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 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 center of gravity, [20] fit within the loading gauge and in China allow double stack trains to run under specially heightened overhead lines. 1,676 mm (5 ft 6 in) broad gauge 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. [21] [22] Indian Railways is able to carry containers double-stacked on standard flat wagons at 100 km/h (62 mph). Experiments with triple-stacked operation using lower, 1,981 mm (6 ft 6 in) containers, were done unsuccessfully in 2006. [23] Experiments in India for double stacking using flatcars under 25 kV AC overhead lines set 7.45 m (24 ft 5+14 in) above rail have begun with funds given by Japan. [24] [25] [26]

See also

Related Research Articles

<span class="mw-page-title-main">Containerization</span> Intermodal freight transport system

Containerization is a system of intermodal freight transport using intermodal containers. Containerization, also referred as container stuffing or container loading, is the process of unitization of cargoes in exports. Containerization is the predominant form of unitization of export cargoes, as opposed to other systems such as the barge system or palletization. The containers have standardized dimensions. They can be loaded and unloaded, stacked, transported efficiently over long distances, and transferred from one mode of transport to another—container ships, rail transport flatcars, and semi-trailer trucks—without being opened. The handling system is mechanized so that all handling is done with cranes and special forklift trucks. All containers are numbered and tracked using computerized systems.

<span class="mw-page-title-main">Intermodal container</span> Standardized reusable steel box used for transporting goods

An intermodal container, often called a shipping container, or a freight container, (or simply “container”) is a large standardized container designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – such as from ships to trains to trucks – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. It is like a boxcar that does not have wheels. Based on size alone, up to 95% of intermodal containers comply with ISO standards, and can officially be called ISO containers. These containers are known by many names: cargo container, sea container, ocean container, container van or sea van, sea can or C can, or MILVAN, or SEAVAN. The term CONEX (Box) is a technically incorrect carry-over usage of the name of an important predecessor of the ISO containers: the much smaller steel CONEX boxes used by the U.S. Army.

<span class="mw-page-title-main">Intermodal freight transport</span> Cargo transport using multiple containers

Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation, without any handling of the freight itself when changing modes. The method reduces cargo handling, and so improves security, reduces damage and loss, and allows freight to be transported faster. Reduced costs over road trucking is the key benefit for inter-continental use. This may be offset by reduced timings for road transport over shorter distances.

<span class="mw-page-title-main">Loading gauge</span> Maximum dimensions for railway vehicles and their loads

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 keep clear of platforms, trackside buildings and structures. Classification systems vary between different countries, and gauges may vary across a network, even if the track gauge is uniform.

<span class="mw-page-title-main">Railway electrification</span> Conversion of railways to use electricity for propulsion

Railway electrification is the use of electric power for the propulsion of rail transport. Electric railways use either electric locomotives, electric multiple units or both. Electricity is typically generated in large and relatively efficient generating stations, transmitted to the railway network and distributed to the trains. Some electric railways have their own dedicated generating stations and transmission lines, but most purchase power from an electric utility. The railway usually provides its own distribution lines, switches, and transformers.

Terra Transport (TT) was the name for the Newfoundland Transportation Division, a wholly owned subsidiary of Canadian National Railway (CN), created in 1979 as a means to organize the company's operations on Newfoundland.

<span class="mw-page-title-main">Flatcar</span> Type of railroad car for transporting large objects, containers, or machinery

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<span class="mw-page-title-main">St. Clair Tunnel</span>

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<span class="mw-page-title-main">Gauntlet track</span> Railway piece that features overlapping rails on the same sleepers

Gauntlet track or interlaced track is an arrangement in which railway tracks run parallel on a single track bed and are interlaced in such a way that only one pair of rails can be used at any time. Since this requires only slightly more width than a single track, all rails can be carried on the same crossties/sleepers. Trains run on the discrete pair of rails appropriate to their direction, track gauge or loading gauge.

<span class="mw-page-title-main">Rail freight transport</span> Practice of transporting cargo by rail

Rail freight transport is the use of railways and trains to transport cargo as opposed to human passengers.

<span class="mw-page-title-main">Beijing–Kowloon railway</span> North-south train route in China

The Beijing–Kowloon railway, also known as the Jingjiu railway is a dual track railway connecting Beijing West railway station in Beijing to Shenzhen railway station in Shenzhen, Guangdong Province.

<span class="mw-page-title-main">Structure gauge</span> Minimum clearance, height and width of railway infrastructure

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 station platforms, tunnels and bridges, and the width of the doors that allow access to a warehouse from a rail siding. Specifications may include the minimum distance from rail vehicles to railway platforms, buildings, lineside electrical equipment cabinets, signalling equipment, third rails or supports for overhead lines.

<span class="mw-page-title-main">Rail transport in Europe</span> Diversity of European railways

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The Berne Gauge or Berne Convention Gauge is an informal but widely used term for the railway loading gauge considered the standard minimum loading gauge in most of Europe. The term arises from the international railway conference held and consequent convention signed in Bern, Switzerland in 1912. The official name of this gauge is the Gabarit passe-partout international, and it came into force in 1914.

<span class="mw-page-title-main">Well car</span> Type of railroad car

A well car, also known as a double-stack car, is a type of railroad car specially designed to carry intermodal containers used in intermodal freight transport. The "well" is a depressed section that sits close to the rails between the wheel trucks of the car, allowing a container to be carried lower than on a traditional flatcar. This makes it possible to carry a stack of two containers per unit on railway lines wherever the structure gauge assures sufficient clearance. The top container is secured to the bottom container either by a bulkhead built into the car — possible when bottom and top containers are the same dimensions, or through the use of inter-box connectors (IBC). Four IBCs are needed per well car. In the terminal there are four steps: unlock and lift off the top containers of an inbound train, remove the bottom containers, insert outbound bottom containers, lock assembly after top containers emplaced. Generally this is done car-by-car unless multiple crane apparatus are employed.

<span class="mw-page-title-main">Longest trains</span>

The length of a train may be measured in number of wagons or in metres for general freight. Train lengths and loads on electrified railways, especially lower voltage 3000 V DC and 1500 V DC, are limited by traction and power considerations. Drawgear and couplings can also be a limiting factor, along with curves, gradients and crossing loop lengths.

<span class="mw-page-title-main">Trailer-on-flatcar</span> Practice of carrying truck semi-trailers on railroad freight cars

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, since one train can carry more than 100 trailers at once. The trailers will be moved by truck from their origin to an intermodal facility, where they will then be loaded onto a train, typically by a rubber tired gantry crane, for the bulk of their journey. Alternatively, trailers may be driven onto the flatcars via ramps by a terminal tractor. Near the destination, the trailers are unloaded at another facility and brought to their final destination by a tractor unit.

<span class="mw-page-title-main">Xiaoshan–Ningbo railway</span> Railway line in China

The Xiaoshan–Ningbo railway or Xiaoyong railway, is a double-track railroad in eastern China between Hangzhou and Ningbo in Zhejiang Province. Its name in Chinese, the Xiaoyong Line, is named after the railway's two terminal stations, Hangzhou South in Xiaoshan District of Hangzhou on the southern bank of Qiantang River, and Ningbo, whose Chinese character abbreviation is yong. The line is 147.3 km (92 mi) long and was originally built in three parts in 1912, 1914 and 1936; rebuilt in 1959, then electrified in 2009. Cities along route include Xiaoshan District of Hangzhou, Shaoxing, Shangyu, Yuyao and Ningbo, all in Zhejiang Province. The Hangzhou–Ningbo high-speed railway runs parallel to the line. The section between Ningbo and Zhuangqiao railway station is proposed to be quadruple-tracked.

<span class="mw-page-title-main">Rail transport in China</span>

Rail transport is an important mode of long-distance transportation in China. As of 2024, the country had more than 159,000 km (98,798 mi)[a] of railways, the second longest network in the world. By the end of 2023, China had more than 45,000 kilometres of high-speed rail (HSR), the longest HSR network in the world.

<span class="mw-page-title-main">Intermodal railfreight in Great Britain</span> The movement of intermodal containers by rail within Great Britain

Intermodal railfreight in Great Britain is a way of transporting containers between ports, inland ports and terminals in England, Scotland and Wales, by using rail to do so. Initially started by British Rail in the 1960s, the use of containers that could be swapped between different modes of transport goes back to the days of the London, Midland & Scottish Railway.

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