Boston — Even deregulation can't stop the rising transportation rate tide, according to Purchasing Magazine. Deregulation and the resulting competition will temper freight rate hikes, but increases will still run at double-digit levels for 1981, the magazine predicts.
Purchasing Magazine's freight rate forecast for the year:
* Trucks. Truckload rates will increase 9.5 to 11 percent overall. The increase won't be as high where competition is strong or wherever new truckload service is available.
* Rails. Rail rates will climb 10 to 12 percent during the year. Rates for traditionally low-rate commodities, which rails claim they are now hauling at a loss or at little or no profit, will increase more sharply -- possibly 15 to 20 percent.
* Oceangoing. The magazine predicts a 10 percent increase in ocean cargo rates. Overtonnage in world shipping is keeping prices down.
* Inland waterways. Purchasing forecasts a 12 to 15 percent rate increase during 1981.
* Airfreight. Rates could go up as much as 15 percent. Airline deregulation has increased competition. Airfreight forwarders are taking a more aggressive, innovative role and commuter airlines are upping their share of the market in line with their increasing role in passenger travel. But higher fuel costs are almost a sure bet in the months ahead, and they will be reflected in freight rate inc rease.