Shipper executives at the conference pledged not to pressure carriers to lower rates despite a weak economy and overcapacity that could present shippers with pricing leverage.

"It is in no one's interest to squeeze down the carrier" to roll back rates, said Phil Marlino, director, transportation market analysis, truck, rail, and logistics solutions for ConocoPhillips Corp., the Houston-based energy giant. Conoco primarily uses railroads and bulk trucking services to move its freight, Marlino said.

Thomas S. Albrecht, managing director for the investment firm Stephens Inc., said he "doesn't see the same commitment" on the part of truckload shippers to drive rates backward. Albrecht said he sensed a "little difference in attitude" among shippers when it comes to pricing.