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Hopper car

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Covered hopper cars carrying frac sand on the BNSF Railway through La Crosse, Wisconsin
Hopper cars may carry hazardous materials, such as this one in the Midwestern United States. Its payload of ammonium nitrate is indicated by the UN number on the diamond-shaped U.S. DOT placard.[1]

A hopper car (US) or hopper wagon (UIC) is a type of railroad freight car that has opening doors on the underside or on the sides to discharge its cargo. They are used to transport loose solid bulk commodities such as coal, ore, grain, and track ballast.[2][3][4] The hopper car was developed in parallel with the development of automated handling of such commodities, with automated loading and unloading facilities.

Hopper cars are distinguished from gondola cars, which do not have opening doors on their underside or sides. Gondola cars are simpler and more compact because sloping ends are not required, but a rotary car dumper is required to unload them. Some "dual-purpose" hoppers have a rotary coupler on one or both ends, so they can be used in both rotary and bottom-dump operations.


Two main types of hopper car exist. Covered hopper cars, which are equipped with a fixed roof, are used for cargo like grain, sugar, and fertilizer, and Portland cement[5] that must be protected from exposure to the weather. Open hopper cars, which do not have a roof, are used for commodities such as coal, which can suffer exposure with less detrimental effect.

Removable canvas covers are sometimes used to protect moisture sensitive commodities in open hopper cars. Closed hopper cars have a metal top with waterproof loading hatches, which provides superior protection.[6] These loading hatches along the top of the covered hopper may be a single long opening along the centerline or a pattern of multiple round or square openings positioned to allow uniform weight distribution when loading the car.

Some covered hoppers have two to four separate bays, with chutes at the bottom to direct unloading contents.


Hopper cars have been used by railways worldwide whenever automated cargo handling has been desired. "Ore jennies" is predominantly a term for shorter open hopper cars hauling taconite by the Duluth, Missabe and Iron Range Railway on Minnesota's Iron Range. The Coke Express, a CSX unit train of hopper cars loaded with coke, with the words "Coke Express" painted on the sides of the hoppers.

Covered hopper grain car

Large unit trains of various grain crops are a common sight in North America, reaching up to 125 cars long. These predominantly haul grain from the large farming areas of the Great Plains to various markets, but a number of unit trains originate from other major farming areas, such as Illinois and Indiana as well as the Canadian provinces of Alberta, Saskatchewan and Manitoba. These trains may originate from a single grain elevator, or may be marshaled in a yard from various locals (short trains which serve nearby industries). The destinations tend to be large flour mills or ports (for export), or they may be split up and delivered to multiple locations. The empty cars may return as a whole train, or may be sent back in smaller quantities on manifest trains (trains which carry just about any type of freight). These trains are used primarily for hauling products such as corn, wheat and barley.


This covered hopper car originally was built in the 1950s for the Atlantic Coast Line Railroad. After the 1967 SCL merger, these cars were fitted with rotary couplers and used in Bone Valley phosphate service.

The word "hopper", meaning a "container with a narrow opening at bottom", goes back to the thirteenth century,[7] and is found in Chaucer's story "The Reeve's Tale" (written late fourteenth century) in reference to a machine for grinding grain into flour.

Historically, open hopper cars were used to carry coarse mined products like coal, ore, and gravel, while boxcars were used for granular materials requiring protection from the elements.

Weatherproof covers were added to hopper cars, creating the covered hopper. Early production emphasized two-bay cars very similar to open coal hoppers and suitable for materials of similar density, like Portland cement or rock-salt. Some cars were available in the 1910s, and became more common by the 1940s. These early cars were volume-limited for less dense commodities like grain or sugar, so later designs include longer covered hopper cars with higher sides and three or more bottom bays.[8] Increasing axle load limits have allowed some of the heavier loads formerly assigned to two-bay hoppers to be assigned to larger, more efficient three-bay hoppers.

Some covered hopper cars retain the conventional centersill as a strength member transmitting compression and tension forces from one car to the next. Beginning in the 1960s, designs distributing these forces along the sides of the car eliminated the centersill beam to simplify bulk material handling with wider hopper openings reducing the tendency for bridging to restrict gravity flow when unloading the car.[9]

Typical American freight car weights and wheel loads[edit]

Common net car loads Gross car weights Wheel loads
Short tons Long tons Tonnes Pounds Kilograms Pounds Kilograms
80 71.4 72.6 220,000 100,000 27,500 12,500
100 89.3 90.7 263,000 119,000 32,875 14,912
101 90.2 91.6 268,000 122,000 33,500 15,200
111 99.1 100.7 286,000 130,000 35,750 16,220
125 111.6 113.4 315,000 143,000 39,375 17,860

Increase in wheel loads has important implications for the rail infrastructure needed to accommodate future grain hopper car shipments. The weight of the car is transmitted to the rails and the underlying track structure through these wheel loads. As wheel loads increase, track maintenance expenses increase and the ability of a given rail weight, ballast depth, and tie configuration to handle prolonged rail traffic decreases. Moreover, the ability of a given bridge to handle prolonged rail traffic also decreases as wheel loads increase.[10] The axle load is twice the wheel load.


See also[edit]


  1. ^ Beaucham, Catherine C. (August 2023). "Evaluation of Potential Exposures to Railway Hazardous Material Inspectors" (PDF). U.S. National Institute for Occupational Safety and Health (Health Hazard Evaluation Report). Retrieved 4 May 2024.
  2. ^ "Covered Hopper Railcars". GATX Corporation. Archived from the original on 16 September 2010. Retrieved 11 September 2012.
  3. ^ "Small Cube Open-Top Hoppers and Gondolas". GATX Corporation. Archived from the original on 16 September 2010. Retrieved 11 September 2012.
  4. ^ "Covered Hopper Cars". Chicago Freight Car Leasing Company. Archived from the original on 16 April 2012. Retrieved 11 September 2012.
  5. ^ Walthers, W. K. (1937). Handbook for Model Railroaders. Wauwatosa, Wisconsin: The Modelmaker Corporation. p. 114.
  6. ^ Henry, Robert Self (1942). This Fascinating Railroad Business (First ed.). New York: The Bobbs-Merrill Company. pp. 248 & 249.
  7. ^ "Hopper". Online Etymology dictionary.
  8. ^ Sweetland, David R.; Horsley, Stephen (1994). Northern New England Color Guide to Freight and Passenger Equipment. Edison, New Jersey: Morning Sun Books. pp. 35, 36 & 51. LCCN 94075695. OCLC 32243319.
  9. ^ "Centerflow Cars". American Railcar Industries, Inc. Retrieved 24 June 2020.
  10. ^ Bitzan, John D.; Tolliver, Denver D. (October 2001). "The Economics of Heavy Hopper Cars". Mountain-Plains.org. Mountain Plains. Archived from the original on 23 July 2011. Retrieved 7 August 2010.

Further reading[edit]

  • Bernard Ciry, "Les wagons-trémies à céréales et à bogies", Rail Miniature Flash, No. 632, Paris, Rigel Editions, June 2018, pages 28–41.

External links[edit]