Source: Intermodal Association of North America & American Association of Railroads.
American Intermodal Rail Traffic, 1988-2016
Rail transport trends in the United States underline a significant shift of intermodal traffic to the advantage of containerized freight. While rail intermodal container traffic (container on flat cars; COFC), both ISO and domestic, increased, the number of trailers carried by rail (trailers on flat cars; TOFC) declined. This represents a significant shift in the TOFC/COFC balance; 55%/45% in 1990 and 9%/91% container in 2016. TOFC has thus become a marginal segment of intermodal transportation used for niche services, most of them point to point.
58% of the containers handled in 2005 were international (maritime) containers, while domestic containers accounted for 23% and trailers 19%. About 25% of all international cargo moved by rail is transloaded into domestic containers. COFC traffic peaked in 2007 and declined in 2008 and 2009 due to declining import demands. As of 2016, intermodal rail traffic recovered, but not to pre-2006-07 traffic levels. This raises the question as if intermodal rail has reached its market potential in the United States or if there is additional growth to be expected.
One of the core advantage of COFC versus TOFC concerns double stacking, involving a  much higher utilization density of rail assets. Several large American trucking companies are also converting to containerization, thus relying on COFC as opposed to TOFC. For instance, in 2009, citing energy and cost advantages, major LTL shipper Schneider National converted its entire intermodal fleet to containers. JB Hunt, with the largest fleet of domestic 53-foot containers, is also converting to COFC operations.