The credit freeze contributing to retail sales of automobiles is also forcing car rental companies to slash their fleet orders, according to Automotive News.

Rental companies bought 1.5 million new cars and trucks in 2008, down from 1.9 million in 2007, according to an estimate by trade publication Auto Rental News. Sales are expected to fall even more in 2009 as rental companies shrink their fleets.

Robert Barton, president of the American Car Rental Association, told Automotive News that many rental companies can’t borrow money to finance the inventories they would like. Also, he said, many franchised dealers cannot get financing to buy retired rental vehicles at auctions.

Enterprise expects to buy 400,000 new vehicles in the 2009 model year, about half the total of recent years. The figure covers rental cars bought for the Enterprise, National and Alamo brands.

Enterprise now keeps its rental vehicles in service for an average of 13 months, up from 11 months, reported Automotive News.

Hertz maintains about 300,000 vehicles in its U.S. fleet. A spokesman told Automotive News that the company is likely to cut back on new-vehicle purchases this year.