Source: Adapted from Coyle, J.J., E.J. Bardi and R.A. Novack (1994) Transportation, Fourth Edition, St. Paul/Minneapolis: West Publishing Company, p. 262.
Piggyback and Doublestack Train Cars
One of the first attempts at piggybacking dates back to 1872 when the Barnum & Bailey Circus used its own special train of flat railroad cars to tour cities in the United States. It took 3 to 5 hours and considerable effort to unload and load trailers, but the concept remained and piggybacking started to be adopted by railroad operators. By the 1950s piggybacking became increasingly used and a good source of income for rail companies.
Containerization however changed from piggybacking to stacking and then to doublestacking where possible. Doublestacking of containers (Container on Flat Car; COFC) saves much more convoy space than the piggyback method (Trailer on Flat Car; TOFC) with the added advantage of not to have to carry a trailer. However, several rail routes are not compatible with doublestacking because of the required height clearance for bridges and tunnels (5.5 meters). Converting a rail line to doublestacking can be a costly undertaking, especially on the much older European rail system where bridge clearances tend to be lower. In North America, such investments are done over high priority corridors.