Thirty-five years ago, the average freight train could safely haul 2,200 tons at once.

That was a lot of cargo!  Even though the basic structure of a train has remained the same, today a single freight train can carry more than ever before — a whopping 3,600 tons, on average. And that’s at rates that are among the lowest in the industrialized world. As a result, America’s railroads pull their own weight in the nation’s integrated transportation network of trains, trucks and barges, which delivers 54 tons of goods and commodities for every American in a single year.

How did freight railroads get so strong?

1. Distributed Power

A locomotive provides the power to move a train forward. So adding multiple locomotives throughout a train means even more power, right? Yes, and more power means trains can carry dramatically heavier tonnages, increasing the efficiency of a single train — a win for rail customers as well as consumers. That is the theory behind distributed power, or the distribution of multiple locomotives throughout a train.

Today, special technology allows these locomotives to coordinate braking and traction power, decreasing stopping distance and enhancing overall safety. In addition to greater power and safety, the technology also reduces equipment damage that can happen when trains are going up steep inclines.  Plus it reduces fuel consumption and rail wear.

2. Lighter Freight Cars

The average coal car can carry approximately 20% more coal than in 1990. That’s because freight railroads have developed and deployed newer, lighter freight cars, replacing many aging steel rail cars with lightweight aluminum cars designed specifically to carry coal. These aluminum cars are about 1/3 lighter than their steel equivalents.

Together with the increased use of lighter weight castings for rail components, railroads have reduced the weight of a train without sacrificing its safety or strength. Equally important, the reduction in the weight of rail cars means railroads can carry more cargo be once. Since most coal trains are 100 cars or more, even a slight reduction in weight for each car can mean significantly larger shipments and greater value for rail customers.

3. Alternating Current Traction Motors

Like a car tire spinning on a patch of ice, steel train wheels can end up spinning in place if a load is too heavy. This spinning can damage the wheels and the rail, often resulting in additional maintenance. The advent of alternating current traction motors provides greater adhesion between a train’s steel wheel and the steel rail, even when carrying large (and heavy) quantities of raw materials like coal and ore. Greater adhesion means more pulling power — allowing railroads to carry heavier loads with fewer locomotives attached to a single train.

4. Double Stacking

In 1977, transport entrepreneur Malcom McLean wanted to find a more efficient way to carry shipping containers by train. So he partnered with Southern Pacific Railroad to create and test the first double-stacked intermodal rail car.

Today, a single train carries as much freight as hundreds of trucks — a feat made possible, in part, by McLean and Southern Pacific’s innovation. And double stacking has double the benefits: first, to the industry and consumers by increasing intermodal efficiency, and second, to the environment by reducing greenhouse gas emissions. Over the years, freight railroads have raised clearances, upgraded tunnels and strengthened rail lines throughout most of America’s 140,000-mile freight rail network to accommodate double-stacked intermodal trains.

5. ‘Heavy Axle Load’ Program

The Transportation Technology Center’s (TTCI’s) Heavy Axle Load Research Program studies ways to safely increase the maximum weight a train can carry. By examining the effects of heavier loads on track and equipment, railroads can improve the design of equipment components and track structure and procedures for inspection and maintenance. The program’s research allowed railroads to implement 36-ton axle loads — an increase of 9% — safely.

More than ever before, freight rail is carrying the weight of the American economy. And through innovations like these, the industry is preparing to carry even more in the years to come.