In North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n railroading, a cow-calf (also cow and calf) locomotive is a set of switcher

Switcher

A switcher or shunter is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been...

-type diesel locomotive

Diesel locomotive

A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

s. The set usually is a pair; some 3-unit sets (with two calves) were built, but this was rare. A cow is equipped with a driving cab; a calf is not. The two are coupled together (either with regular couplers

Coupling (railway)

A coupling is a mechanism for connecting rolling stock in a train. The design of the coupler is standard, and is almost as important as the railway gauge, since flexibility and convenience are maximised if all rolling stock can be coupled together.The equipment that connects the couplings to the...

 or a semi-permanent drawbar) and are connected with MU

Multiple-unit train control

Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train from a single location, whether it is a Multiple unit comprising a number of self-powered passenger cars or a set of locomotives.A set of...

 cables and brake lines so that both locomotive units can be operated from a single cab.

Cows are analogous to A unit

A unit

An A unit, in railroad terminology, is a locomotive equipped with a driving cab, or crew compartment, and the control system to control other locomotives in a multiple unit, and therefore able to be the lead unit in a consist of several locomotives controlled from a single position...

s and calves to B unit

B unit

A "B" unit, in railroad terminology, is a locomotive unit which does not have a driving cab, or crew compartment, and must therefore be controlled from another, coupled locomotive with a driving cab . The term booster unit is also used. The concept was largely confined to North America...

 road locomotive

Road locomotive

Road locomotive could refer to:* A type of traction engine, usually referring to those designed for heavy haulage on common roads...

s. Like the early EMD FT

EMD FT

The EMD FT was a diesel-electric locomotive produced between November 1939, and November 1945, by General Motors' Electro-Motive Division . All told 555 cab-equipped A units were built, along with 541 cabless booster B units, for a grand total of 1,096 units. The locomotives were all sold to...

 locomotives, the Cow-calf sets were typically built as mated pairs, with the Cow (or cabbed unit) and calf (or cabless unit) sharing a number. However this was not always the case, with over time many of the sets being broken up and couplers added to aid with versatility.

Most cow-calf sets were built between the 1930s and the 1950s. They were built by several different makers, although General Motors' Electro-Motive Division built far more than the others. As originally constructed, the cow-calf units were typically used in hump yards where they spent much of their life pushing long trains over the hump for classification. There were, however, a few notable cases where this was not so, with some industrial railroads using non mated pairs as light road switcher locomotives. However as with the larger three unit Cow-calf sets, such was very rare.

The cow-calf concept was adopted on Queensland 2ft gauge sugar cane railways with two locomotives being coupled permanently in multiple-unit mode with the cab of one removed. This was utilised by Isis Mill (1980-1993) and by Mackay Sugar (2005).

The concept was also used in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 by British Rail

British Rail

British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...

 to produce the unique Class 13

British Rail Class 13

The British Rail Class 13 were created in 1965 because of a necessity to provide more powerful shunters for the Tinsley Marshalling Yard. This was achieved by permanently coupling together two Class 08 shunters as a 'master and slave' units, the latter with its cab removed...

 locomotives, composed of two Class 08 locomotives. British terminology is Master-and-Slave Unit.

Cow-calf locomotives can be distinguished from the sometimes very similar looking slug

Slug (railroad)

A railroad slug is an accessory to a diesel-electric locomotive. It has trucks with traction motors but is unable to move about under its own power, as it does not contain a prime mover to produce electricity...

 and slug mother sets by the fact that both cows and calves are independently powered, while slugs are engineless, and dependent on power from their "mother" units.

List of cow-calf models

• EMD TR
• EMD TR1
  EMD TR1
  The EMD TR1 was a two-unit "cow-calf" diesel locomotive built by General Motors Electro-Motive Division of La Grange, Illinois in 1941. Two pairs were built for the Illinois Central Railroad, the only purchaser....
  
  
• EMD TR2
• EMD TR3
• EMD TR4
• EMD TR5
• EMD TR6
• ALCO SSB-9
• Baldwin S-8
  Baldwin S-8
  The Baldwin S-8 was an 800-horsepower diesel-electric locomotive intended for use in yard switching. The Baldwin Locomotive Works produced a total of 54 units between 1951 and 1953. In addition, nine "calf" units were built for Oliver Iron Mining Company in Minnesota...
  
  
• British Rail Class 13
  British Rail Class 13
  The British Rail Class 13 were created in 1965 because of a necessity to provide more powerful shunters for the Tinsley Marshalling Yard. This was achieved by permanently coupling together two Class 08 shunters as a 'master and slave' units, the latter with its cab removed...
  
  
• Russian TGEM10