Married pair
Encyclopedia
A twinset or twin unit is a set of two railroad cars or locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

s which are permanently coupled and treated as if they were a single unit. A twinset of cars or coaches can also be called a twin car.

USA

In US passenger railroad parlance, twin units are also known as Married pairs. On passenger railroads, light rail
Light rail
Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems...

, and monorail
Monorail
A monorail is a rail-based transportation system based on a single rail, which acts as its sole support and its guideway. The term is also used variously to describe the beam of the system, or the vehicles traveling on such a beam or track...

 services, married pairs may have machinery necessary for full operation of the cars split between them. Items that are typically shared include transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...

s, motor controller
Motor controller
A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and...

s, dynamic braking
Dynamic braking
Dynamic braking is the use of the electric traction motors of a railroad vehicle as generators when slowing the Locomotive. It is termed rheostatic if the generated electrical power is dissipated as heat in brake grid resistors, and regenerative if the power is returned to the supply line...

 grids, cabs and current collectors
Pantograph (rail)
A pantograph for rail lines is a hinged electric-rod device that collects electric current from overhead lines for electric trains or trams. The pantograph typically connects to a one-wire line, with the track acting as the ground wire...

. This provides significant savings in both cost of equipment and weight, which increases performance and decreases energy consumption. The cost is slightly higher operating cost
Operating cost
Operating costs can be described as the expenses which are related to the operation of a business, or to the operation of a device, component, piece of equipment or facility.-Business operating costs:...

s incurred when the extra car of a pair is not necessary for the level of service.
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