NEW YORK — Motor freight rates remain on the rise, climbing at much as 10%, despite generally stagnant cargo volumes, as carriers focus on pricing and effectively match capacity to demand, six top industry officials said at a recent investment conference.

The lackluster economy, combined with widespread weather troubles that delayed and reduced produce shipments, have sharply reduced refrigerated freight so far this year,  industry experts have said.

TransCore’s North American freight index for July marked the seventh straight record, the company said.

Rising demand for freight hauling is generating more business for trucking companies, but rising costs and a dwindling supply of drivers are making it difficult for the nation’s top for-hire carriers to provide additional capacity to meet that demand.

The Cass Freight Index, which measures freight bills paid for shipments moved primarily by truck, rose 9.6% in May from the same month a year ago, but the latest report showed a slow-down in the growth pace tied to the economy.

LAS VEGAS — Freightliner Trucks introduced two new severe-duty trucks last week at the 2011 ConExpo/ConAgg construction conference and equipment exhibition here, in a move by Daimler Trucks North America to recapture market share in vocational vehicles.