Married pair

A twinset or, in US parlance, married pair, is a set of two railroad cars which are permanently coupled and treated as if they were a single unit. On passenger railroads, light rail, and monorail services, married pairs may have machinery necessary for full operation of the cars split between them. Items that are typically shared include transformers, motor controllers, dynamic braking grids, cabs and current collectors. This provides significant savings in both cost of equipment and weight, which increases performance and decreases energy consumption. The cost is slightly higher operating costs incurred when the extra car of a pair is not necessary for the level of service.

Types of Married Pairs

Married Pairs present a variety of options regarding their couplings and equipment layout. Railfans and industry professionals alike have extended the term along the general theme of marriage.

*Civil Unions - These units are mechanically single units with a complete set of equipment on each train and standard couplers between every car. While able to operate alone the cars may only have one cab or no cabs at all, requiring to be paired up for normal operation. All PATH rolling stock is of the civil union variety.

*Protestant Married Pairs - These units are the most common variety of married pair in that components are shared between cars and the coupler are of a semi-permanently type which cannot be separated in normal operation. However, with some effort the cars can be broken apart and re-paired with other units.

*Catholic Married Pairs - This consist of articulated units which share wheelsets and thus cannot be separated without a great deal of effort. Most modern trams and light rail vehicles are of the Catholic variety.

*Mormon Married Pairs - This is a married pair consisting of more than two units. While similar to a standard railroad trainset, Mormon married pairs are still regularly combined into larger trains. The New York City Subway is the largest user of the Mormon married pair initially converting their protestant married pair R44, R46 and R68 units into 4 or 5 car Mormon married pairs. All new car orders have been of the Mormon variety.