The idea of intermodal transportation dates back to the Nineteenth Century. Trailer on Flat Car (TOFC) service as we recognize it today began its surge in the 1950s. But it was the rise (literally) of the double-stack container cars in the 1980s that propelled intermodal to the number 2 spot in railroad revenue earnings – where it has remained ever since.
Shipping containers offer the utmost in flexibility for transport and storage. They can be loaded on ships, trucks or trains, and stacked to save space. Although many different sizes and options are available, there is enough standardization in the industry to allow easy interchange. Without any need of mechanical systems (except for refrigerated units,) containers are cheap to build and maintain.
Since containers require less vertical clearance and offer a lower tare weight than trailers, the flat cars designed for TOFC service weren’t as efficient for containers (COFC). The Southern Pacific worked with American Car and Foundry to design the first car that would more than double the capacity of the car by stacking containers 2-high. By lowering the floor of the car closer to the rail, the double stack was able to clear more tunnels and bridges. This also greatly lowers the cars’ center of gravity. By building multiple well cars sharing articulated trucks, weight and friction are further reduced.
Initial designs used large bulkheads to hold the upper containers in place. Within a few years it was determined that the same interbox connectors (IBC’s) used on board ships would also hold the containers on rails. The elimination of the bulkheads further reduced the weight and center of gravity of the car and freed up space on the upper deck for ever-lengthening domestic containers.
At first the stack trains were confined to a very limited number of routes. Since the advantages of the service have been proven, railroads have invested billions in raising clearances on more lines. Today’s Norfolk Southern Heartland Corridor project is a good contemporary example.
Today’s double stack loads fall into one of two categories. International shipments are transloaded at ports on either North American coast. Many of these loads are bound from Asia to European markets are never unloaded on US soil. The vast majority of international shipments travel in 40 foot containers. International containers can also be 20 or 45 feet long. International containers are often brightly colored with large company slogans. Domestic (North American) shipments make up a larger and larger share of the revenue every year. With larger clearances on highways, domestic containers can be as long as 53 feet. All share a common set of 40′ posts however, allowing them to be stacked with international containers. Beginning in the early 1990s, large trucking shippers like JB Hunt began purchasing fleets of containers in addition to trailers to maximize intermodal utilization.
You can model a double stack train on your layout too. Depending on the train, you can find solid or mixed consists of international and domestic loads using both well cars and also single level spine cars. Although becoming increasingly rare today, you can even find a few conventional flat cars in service. Running on the hottest schedules, these colorful trains are today’s streamliners and the pride of the railroads. Let one loose on your rails!