Trains have long been a more fuel-efficient way to haul freight than trucks, but now the federal government's amped up support in the alternative energy arena may help "the iron horse" go even greener with hybrid locomotives and other advances.

Although large freight railway traffic (measured in carloads) is down 19 percent this year due to the recessed economy, it grew 47 percent between 1990 and 2007, and railroads have been more fuel-efficient than trucking for at least the past few decades, according to the Association of American Railroads.

The average train in 1980 used four liters of fuel to move one ton of freight 380 kilometers, and by 2007 the average increased to 700 kilometers, or three times the fuel efficiency of a truck, says Steven Forsberg, general director of public affairs with BNSF (Burlington Northern Santa Fe Railway) in Fort Worth, Tex.

New hybrid locomotives are designed to do even better, trading on the same technologies found in today's hybrid automobiles. General Electric uses a regenerative braking technology in its trains similar to that found in a Toyota Prius. The Mercedes-Benz Citaro fuel-cell transit bus set the stage for railroad energy-efficiency systems being created by hydrogen fuel-cell technology company Vehicle Projects, Inc. in Golden, Colo. And the Chevrolet Volt is the basis for an ethanol-based hybrid under development by Milford, Ohio–based Alternative Hybrid Locomotive Technologies, Inc. (AHL-TECH).

"The use of hybrid locomotives can reduce locomotive exhaust emissions and energy consumption, while providing an adequate or equitable amount of power to operate trains," says Warren Flatau, a spokesman for the U.S. Department of Transportation's (DOT) Federal Railroad Administration.

View a slide show featuring green train technology

Pros and cons
The challenges that arise in developing hybrid locomotives—such as power density and durability—are the same as in cars, but on a bigger scale because of the heavy load and harsh vibrations associated with rail freight, says Glen Merfeld, manager of GE Global Research's chemical energy systems lab.

Hybrid locomotive technologies offer many advantages, but they will come with new obstacles, says Mike Iden, general director of car and locomotive engineering at Omaha, Neb.–based Union Pacific Railroad, the nation's largest railroad company, with a 5,150-kilometer network.

"In reality there is no single fuel that will satisfy what we need and want," Iden says. Supporting a rail system powered by hydrogen fuel cells, for example, would require an entirely new infrastructure because hydrogen, being a small molecule, would leak through existing pipelines. Also, railroads currently do not receive specific incentives to use alternative fuel, the DOT's Flatau adds.

Reliability and safety may also be an issue. RailPower Technologies Corp.'s Green Goat diesel–electric "switcher"—a small, short-distance locomotive for assembling, disassembling and moving trains in rail yards—was a promising technology powered primarily by batteries (even when it idled) and employed its diesel engine only to recharge the batteries. Unfortunately, the Green Goat's batteries are known to have caught fire, forcing RailPower to recall, retrofit and update 59 units of the locomotive in May 2007, a move that cost the company about $15.5 million for warranty provisions. Nicholasville, Ky.–based R.J. Corman Railroad Group, LLC, acquired RailPower in June (pdf). Although the Green Goat's future is uncertain, there is "no doubt in my mind" that hybrids will be part of the mix in the future, says Bruce Greinke, chief operating officer of R.J. Corman.

Although the cost of research and development makes hybrids more expensive than conventional counterparts, rail experts agree that the savings achieved by improved fuel efficiency can provide quick return on investment. In 2006 a 2,000-horsepower Green Goat cost about $750,000 compared with $450,000 for a typical refurbished diesel switcher, according to It was also more expensive than installing idle-control technology alone, which goes for about $33,000, according to the U.S. Environmental Protection Agency (EPA) (pdf), but saved far more fuel, according to a report by the U.S. Department of Energy's Argonne National Laboratory. (pdf)

Other ways to green the rails
Hybrids will be paired with other advancing technologies to produce the green railways of the future. Government agencies such as the Energy Department and the EPA are partnering with companies to develop low-sulfur diesel and biofuels.

"It's a combination of cleaner fuel, advancements to the engine, and the use of emissions control technology," says Allen Schaeffer, executive director of the Diesel Technology Forum, an organization supporting the use of clean diesel technology.

A movement for full electrification of passenger railways is also emerging, which has thus far been hindered by the extravagant cost of infrastructure—$6 million to $8 million per mile, says Arnold Miller, president of Vehicle Projects, a company developing prototype fuel-cell vehicles.

The DOT, passenger rail-operating authorities, the American Public Transportation Association, manufacturers, and other investors are developing an electric-drive strategy that would increase the use of electrically powered road and rail applications, Flatau says.

"Hybridization is one of the ways we can tie into alternative forms of energy and more efficiently use our fuel resources," Merfeld says. "This is just the beginning."