New York--In the newest phase of its expanding focus on b-to-b, DoubleClick Inc. has entered into an expansive deal with AutoTrader.com L.L.C. to market to auto manufacturers. Atlanta-based AutoTrader.com, the Internet's largest automotive marketplace, is joining DoubleClick's Media Network; DoubleClick will have the exclusive rights to sell advertising across AutoTrader.com's certified and new vehicle programs. Separately, AutoTrader will begin using DoubleClick's AdServer software. While business-to-consumer online automotive dealing has been taking root for years, b-to-b transactions are still in their infancy, despite efforts of industry leaders including Covisint L.L.C.