Truckload and logistics giant Schneider National Inc. said Tuesday it has signed a multiyear agreement with Eastern railroad CSX Transportation to expand their intermodal transportation partnership in the heavily congested Eastern region of the United States.

The agreement "sets the stage for sustained, long-term service within the Eastern United States as Schneider's intermodal freight volumes continue to increase," Green Bay, Wis.-based Schneider said in a statement.

Schneider said the agreement, which builds on a partnership first reached in 2008, would open up more Eastern points on CSX's network for Schneider to serve. In the statement, Schneider said the expanded agreement would offer its customers "capacity, operational interfaces, and access to preferential loading in some circumstances that will increase accessibility and efficiency of rail moves."

"We're recommitting the expertise of one of the nation's major railroads and one of the largest intermodal providers at a time when truckload capacity is getting tighter and shippers need creative new solutions to move freight," said Bill Matheson, president of Schneider's intermodal services unit.

"The current economic conditions and business environment tell us there will be more interest than ever in finding cost-effective, reliable modes for moving freight," added Bill Clement, vice president-intermodal for CSX Transportation.

Schneider said the agreement would expand capacity in East Coast and Midwest markets, where shippers are expected to struggle to procure over-the-road trucking space due to a shortage of qualified truck drivers.

The agreement is another step in a grand plan by the nation's five major railroads to convert over-the-road freight of virtually any length of haul to domestic intermodal service. Jacksonville, Fla.-based CSX told analysts in mid-2011 that of the 14 million truckloads that normally move in the Eastern United States each year, about 5.1 million have already been converted to intermodal, leaving a potential market of somewhere around 9 million.

CSX said it handles about 40 percent of the 5.1 million loads that have already been converted to intermodal.