"Piggyback" trains are the hottest things on rails today. While the roots go back more than a century, the truck-rain service revolution really began in the 1950s. So for most of the most popular modeling eras, these cars and trains are an important part of the scene.
TOFC or Trailer On Flatcar is one of the most basic forms of intermodal transportation. The concept of loading trailers onto flatcars dates to the mid-1800s. The concept was adopted by the circus and military before coming into its own with the rise of commercial trucking in the 1950s.
Several railroads pioneered new TOFC services in the 1950s. The concept allowed trucks to handle the door-to-door deliveries with railroads taking the load for the long haul. Initially, many railroads tried putting small ramps in many towns. Larger "hubs" quickly proved more efficient. Intermodal terminals today are still called "ramps" even though cranes have long since replaced loading ramps.
Early operations used "circus-style" loading, where trailers were backed onto the flatcars from one end. Special bridge plates were lowered between cars to allow the trucks to cross. This process originated from circus operations, and it was time-consuming and challenging with long cuts of cars. Only one trailer could be loaded at a time and backing the trailer required significant skill.
Once in place, trailers had to be secured with chains and wheel chocks. At the destination, the train had to be spotted at the ramp with the trailers facing the ramp so that tractors could tie on to unload. This meant that most terminals needed a wye nearby to turn cars.
As terminals expanded in the 1960s, cranes and lifts and new fifth-wheel couplings sped loading and unloading operations greatly. These facilities could also often handle shipping containers as well as trailers.
Early operations often relied on standard 40 and 50-foot flatcars to haul trailers. Longer cars designed for TOFC operation in the 1950s were 75 feet. These could haul two standard 35' trailers of the day.
TOFC flatcars were usually equipped with drop plates on the ends and places to attach the tie-down chains on the sides and centers. Rub rails along the sides were also sometimes used to prevent a trailer from rolling off during loading.
As trailers grew to 40-foot standard lengths, flatcars also grew to 85 and later 89 feet. The latter was useful even after 45-foot trailers became common in the 1980s. The rise of 48 and then 53-foot trailers in the 1990s meant that only one could be handled on a typical 89 foot flat. A variety of hitch arrangements allow different trailer and container combinations. Flatcars not adapted for today's long trailers can be seen hauling other loads as well.
Spine cars offered reduced length and weight and greater flexibility than flats. With a smaller platform size, these cars were lighter. Three and five-unit articulated cars offered greater efficiency by reducing coupler slack and wheels.
Cars are normally used for containers, but some have hitches for trailer use as well. This flexibility allows equipment in intermodal pools to carry whatever load is needed.
Trailer Train (TTX)
The high cost and national nature of intermodal markets enticed railroads to pool their resources when purchasing equipment. Trailer Train Corporation was created in 1955 to supply intermodal flatcars to the railroads that invested in it. This shielded the railroads themselves from the investment cost if the new technology failed. It also provided more seamless service across multiple roads and encouraged standardization and cooperation between competing lines.
Renamed TTX Corporation in 1991, the company's yellow flat, spine, and well cars are seen in almost every intermodal train. The company also supplies flat cars for autoracks and other uses and is the parent company for the Railbox and Railgon boxcar and gondola pools.
In addition to Trailer Train, many railroads own their own equipment which is often pooled to operate nationally.