Articulated “spine cars” are a common sight on North American mainlines today as they carry trailers and containers in priority intermodal trains. While their use has exploded in recent decades, the history of this “bare bones” car goes back much further.
The earliest spine cars weren’t used to haul trailers or containers. In fact, they were about as far from the high-speed freight intermodal market as you could get! Used by logging companies as early as the late Nineteenth Century, the basic spine car offered a vehicle with a minimum light weight and easy unloading of large logs.
Simple to build, these cars were not much more than trucks and a center frame or “spine.” Cross beams over the truck helped support the log loads. Stacked and chained down at the logging camp, once the logs arrived at the mill unloading was a simple matter of unbuckling the chains and tipping or pushing the logs off and into the mill pond.
Eliminating the cost, weight and maintenance of a flatcar deck made sense in this service. It would be many decades however before the idea found a practical use in common carrier rail lines.
The first uses of spine cars in intermodal service began in the late 1960s with projects like the Clejan car on the New Haven and Southern Pacific and the better-known Flexi-Van cars on the New York Central and several other railroads. Like the logging spine cars, the basic premise behind these designs was to reduce the weight and cost, and inefficiencies of the flatcars currently used in Trailer on Flatcar service.
These pioneering spine cars were similar in length to the longer flatcars then in service for hauling trailers, 75 feet. Of course you couldn’t load these cars the same way you’d load a conventional flatcar, and therein lay the real drawback to the designs. The FlexiVan car used a turntable on the spine to pivot the container load so that no special cranes were needed. But this had its own set of problems from extra maintenance and complexity on the cars to a need for empty chassis at each terminal. For the efficiencies of the cars to be realized, railroads would also have to redesign the terminals and purchase new equipment to load and unload the spines.
As intermodal trains continued to evolve into longer-haul services from fewer dedicated hubs in the 1970s, the climate improved for alternatives to the flatcar and conventional “circus style” loading. In the 1980s, the first new spine car to have a major impact was the “Front Runner” – a single unit car whose construction took minimization to the extreme. The central spine had two platforms attached at one end to support the trailer’s wheels. It rode on two axles with only 28″ wheels to lower the total height. The cars were light – too light – and were prone to derailments, especially when running empty and mixed in with heavier, traditional equipment.
The advantages of this reduced design were apparent however and railroads, car builders and Trailer Train all partnered to bring new designs to the rails. By the end of the 1980s, the five-unit articulated spine car emerged as the new standard. Articulation allowed use of conventional trucks while further reducing weight and coupler slack in a train. While some early spine cars were trailer only or container only, dual-capacity cars soon emerged for greater flexibility and fleet utilization.
Since then, the overall form of these cars has changed little. The most consistent change was an ever-increasing length of the individual cars to accommodate longer trailers. Today both three and five-unit cars are common. Together with the double-stack container well cars, these platforms form the “backbone” of the North American intermodal fleet.