A railroad crane (North America: crane car or wrecker; UK: breakdown crane) is a type of crane used on a railroad for one of three primary purposes: freight handling in goods yards, permanent way (PW) maintenance, and accident recovery work. Although the design differs according to the type of work, the basic configuration is similar in all cases: a rotating crane body is mounted on a sturdy chassis fitted with flanged wheels. The body supports the jib (UK; North America: boom) and provides all the lifting and operating mechanisms; on larger cranes, an operator's cabin is usually provided. The chassis is fitted with buffing (UK) and/or coupling gear to allow the crane to be moved by a locomotive, although many are also self-propelled to allow limited movement about a work site. For cranes with a jib that extends beyond the length of the chassis, an idler car (also known as a 'jib carrier' (UK) or 'boom car' (North America)) is provided to protect the jib and to allow the crane to be coupled within a train. The idler car is usually a long, flat wagon (i.e. a flatcar) that provides a means of securing the jib for transportation; storage areas for special equipment or supplies are usually fitted too. It was not uncommon for the idler car to be built on a withdrawn revenue-earning wagon, such as on the Great Western Railway after the Grouping and in the 1930s (where they were referred to as 'match trucks'). Usage Railroad cranes are usually designed specifically for one of three purposes: Goods yard cranes Usually the smallest of the railroad cranes, goods yard cranes were used in the larger goods yards to provide lifting capability in areas away from the ground-mounted goods cranes normally provided in such yards. They were often small enough to be operated by hand, and were not normally self-propelled, instead requiring the use of a shunting engine to move them into position. Once cheap road-going mobile cranes were available, these superseded the rail-mounted variety due to their greater flexibility and mobility. Maintenance cranes The most varied forms of crane are used for maintenance work. General purpose cranes may be used for installing signalling equipment or pointwork, for example, while more specialised types are used for track laying. Breakdown cranes The largest cranes are used for accident recovery work, usually forming part of a breakdown train that includes staff