Double-stack car

A double-stack car, also called a stack car for short, or a well car due to its shape, is a type of railroad car specially designed to carry intermodal container freight. As the name implies, double-stack container cars are built to carry two containers per unit, one stacked on top of the other. This is made possible by the "well", a depressed section which sits between the wheel trucks of the car, close to the rails, allowing a container to be carried lower than on a traditional flatcar. On routes with sufficient clearance (loading gauge), an additional container may be stacked on top of the first one. The top container is held in place either by a bulkhead built into the car, or through the use of inter-box connectors.

Advantages to using double-stack cars include better stability due to the lower center of gravity of the load, lower tare weight, and in the case of articulated units, reduced slack action.

Double-stack cars are most common in North America, where intermodal traffic is heavy, and electrification is less widespread and thus overhead clearances are typically more manageable.


Southern Pacific Railroad (SP), along with Malcom McLean, came up with the idea of the first double-stack intermodal car in 1977.Cudahy, Brian J., - [ "The Containership Revolution: Malcom McLean’s 1956 Innovation Goes Global"] . - "TR News". - (c/o National Academy of Sciences). - Number 246. - September-October 2006. - (Adobe Acrobat *.PDF document)] [ [ Chronological History] - Union Pacific Railroad Company] SP then designed the first car with ACF Industries that same year. [Kaminski, Edward S. (1999). - "American Car & Foundry Company: A Centennial History, 1899-1999". - Wilton, California: Signature Press. - ISBN 0963379100] [ [ "A new fleet shapes up. (High-Tech Railroading)"] . - "Railway Age". - (c/o HighBeam Research). - September 1, 1990] At first it was slow to become an industry standard, then in 1984 American President Lines, started working with the SP 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 SP to Conrail.

Multiple unit cars

Double-stack cars may be constructed with a single well, but are often constructed with multiple units, usually with 3 or 5 wells, connected by articulated joints. Articulated joints are supported by a single wheel truck, (often a 125-ton capacity truck).

Also, in a number of cases, multiple single-well cars (usually 3 or 5) are connected by drawbars and share a single reporting mark.

On both types of multiple-unit cars, the units are typically distinguished by letters, with the unit on one end being the "A" unit, and the unit on the other end being the "B" unit. All railroad equipment has an 'A' and 'B' end, with the 'B' end being the end where the brake wheel (and equipment) is located. On three- and five-unit articulated well cars, the middle units are referred to as 'C', 'D', and 'E'.

Carrying capacity

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 40', 48' and 53' are most common. A number of 45' wells and 56' wells also exist. (The sizes of wells are frequently marked in large letters on the sides of cars to assist yard workers in locating suitable equipment for freight loads.)

In cases where wells are smaller than some of the containers being loaded, larger containers are often placed on top of smaller containers that fit in the available wells. Many wells are also capable of carrying two 20' ISO containers in the bottom position.

Some double-stack cars have been also equipped with hitches which allow them to carry semi-trailers as well as containers. These are known as "all-purpose" well cars.

Other countries

* Australia - double stack trains operate between Adelaide, Perth, Parkes and Darwin.
* India - operates double stack diesel trains on 1676mm gauge using flat cars. []
* India - experiments for 25kV AC double stacking [ ]
* China - double stacked container trains using overhead electricity cables. []

Choke points

Low bridges and tunnels in various locations limit the operation of double stack trains. [ [ Railpage Australia™ - U.S. rail network facing congestion 'calamity' ] ]


Online rosters

* [ Double Stack Cars] - A list of double stack cars by reporting mark, with various data
* [ RR Rolling Stock Category: Double Stack Car] - Picture Archives

Magazine articles

* "Mainline Modeler"::: Fortenberry, Curt & Bill McKean. - "APL Container Car". - February 1987. - p.65-69.:: Fortenberry, Curt & Robert L. Hundman. - "APL container car part II the brake system". - March 1987. - p.78-81.:: Hundman, Robert L., & Curt Fortenberry. - "APL 45-foot container car". - May 1987. - p.54-57.

* "Model Railroader"::: Durrenberger, Cyril. - "SP/ACF double stack cars". - October 1983. - p.83-93.

* "Model Railroading"::: Bontrager, David A. - "Articulated double stacks: a prototype overview". - June 1993. p.24-29.:: Bontrager, David A. - "The Newest Prototype Well Cars: An Abundance of Kitbashing Possibilities". August 1997. - p.46-49.:: Casdorph, David G. and Ed McCaslin. - "Gunderson's Husky-Stack: The Prototype and Detailing A-Line's HO Model". - October 1995. - p.32-37.:: Casdorph, David G. - "NSC 53' Drawbarred Well Car Roster and Pictorial". - August 2002. - p.30-33:: Geiger, Doug. - "Thrall Double-Stacks: Three-Well DTTX Drawbar-Connected Car". - October 1994. - p.50-55.:: Geiger, Doug. - "Gunderson Husky Stack Three-Well BN Drawbar-Connected Car". - July 1995. - p.48-53.:: Geiger, Doug. - "Gunderson Maxi-Stack IIIs Part I: The Prototype". - December 1995. - p.58-63.:: Geiger, Doug. - "Maxi-Stack Well Car Part I: The Prototype". - April 1997. - p.28-31.:: Mansfield, Jim. - "Thrall Five-Unit Double-Stack Car - Series TWG50J". - October 1993. - p.19-23.:: Mansfield, Jim. - "Thrall Five-Unit Double-Stack Car - Series APLX 5000". - November 1993. - p.24-25, 27-31.

*"Railroad Model Craftsman"::: Panza, Jim & Chuck Yungkurth. - "Thrall's double-stack cars". - January 1989. - p.89-98.:: Panza, Jim & Bruce Keating. - "The Gunderson Husky-Stack well car". - July 1992. - p.71-75.:: Panza, Jim & William Halliar. - "Thrall stand-alone and drawbar connected well cars". - October 1992. - p.64-68.

External links

* Double Stack Intermodal Cars-Freight [ doublestackinter]

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