Source: adapted from T. Prince (2001) “Towards an international intermodal network”, American Shipper, November.
An important shift in the composition of the North American intermodal rail fleet took place in the 1990s with the move away from piggybacking (Trailer on Flat Car; TOFC) towards Containers of Flat Car (COFC). The development of long-distance corridors linking major port gateways such as Los Angeles / Long Beach to inland destinations incited the setting of double-stacked unit train services. TOFC services that used to dominate have become marginal. This is related to more efficient usage of rail assets permitted by double-stacked services as well as the commitment of trucking companies to integrate their drayage services with long-distance intermodal rail services. Also, most well cars can accommodate 53-foot domestic containers, undermining the need for piggybacking. What used to be carried as TOFC is now carried as COFC.