Warren Buffett says his railroad buy is an investment in America, but it's also a bet on a recovery in global trade.

Burlington Northern Santa Fe Corp. is the nation's top railroad in intermodal transportation, in which container cargoes move from ships to rail cars to trucks and back again. The nation's biggest container ports are in Southern California, where BNSF trains load up millions of containers of Asian goods each year for inland markets like Dallas-Fort Worth.

Terrance Pohlen, director of the Center for Logistics Education and Research at the University of North Texas, said intermodal is the future.

"Looking down the road a few years, with everybody's views on what's likely to happen with fuel prices and congestion, intermodal is the long-term solution," Pohlen said.

Container traffic has plunged during this recession. The ports of Los Angeles and Long Beach recently reported their worst September in nine years.