This has been a busy year indeed for the Teamsters. In January, the union signed a five-year contract with UPS, and in February, it worked out a five-year deal with trucking conglomerate YRC Worldwide that covers Yellow, Roadway, USF Holland, and New Penn.

In April, the union claimed victory in its decades-long effort to organize the former Overnite Transportation as employees of the renamed UPS Freight voted for their first national contract. According to the Teamsters, the contract brings 9,900 new members into the Teamsters' fold. Union President James Hoffa called it "the largest organizing victory in the freight industry in 25 years." Not all employees who are eligible to join have signed cards requesting membership, and Hoffa vowed to continue efforts to sign up some 3,000 more UPS Freight workers.

And just last month, DHL signed a five-year contract with the union that covers about 10,000 employees. According to DHL executives, the new contract gives the company "increased operational flexibility ... to enhance labor resources management." The union, meanwhile, got substantial annual increases in wages and benefits.

Union leaders acknowledged that DHL's losses since entering the U.S. domestic market complicated the negotiations. But both sides will benefit from the resulting contract, said Brad Slawson, co-chair of the Teamsters' national negotiating committee. "Not only were we able to negotiate significant economic gains for members, this agreement provides job security by allowing DHL to better compete in this tough industry," he said in a statement.

Shippers that depend on unionized carriers can sit back and relax for a while: All of the contracts signed this year remain in force until 2013.