With 85 percent of domestic freight moving by truck and train, one of the big questions facing transportation planners is how to avert epic gridlock as rising traffic slowly overwhelms the nation's freight infrastructure. The Department of Transportation (DOT) believes an underutilized channel might provide some relief. To that end, it's promoting efforts to shift some of the container traffic to "marine highways"—or the nation's coastal and inland waterway system.

Last fall, the DOT's Maritime Administration awarded $4.85 million in grants to projects aimed at expanding the use of navigable waterways. Among the beneficiaries is the Mississippi River, which will receive more than $800,000 to fund initiatives to increase container-on-barge traffic along the storied waterway. The money will be used to boost freight volumes at the Port of St. Louis, Mo., and America's Central Port in Granite City, Ill.

The additional freight capacity will be needed to keep up with demand in the region, which is expected to swell 45 percent by 2050, said a spokesman for the Mississippi River Cities & Towns Initiative (MRCTI), one partner in the project. "The only way to [handle congestion] is either build a bunch of new roads, a bunch of new bridges, and a bunch of new rail, which there doesn't seem to be an appetite for at the national level. Or we use something we already have sitting there waiting, which is the nation's inland waterway system," MRCTI Executive Director Colin Wellenkamp told St. Louis Public Radio.

Other grants in the package include:

• $1,758,595 for the Port of Baton Rouge and Port of New Orleans shuttle service,
• $1,632,296 for the New York Harbor and its container- and trailer-on-barge service,
• $476,748 for the Port of Virginia's James River Container Expansion Project, and
• $173,361 for the Northern Virginia Regional Commission's Potomac River Commuter Ferry Project, which is aimed at giving both commuters and shippers more transportation options.