The United States Postal Service (USPS) said on May 14, 2004 it would replace its fleet of about 2,000 Class 8 tractors in 2005, Calstart reported according to an article in Transport Topics. The USPS noted that its normal eight-year replacement cycle would enable the federally owned corporation to bypass the Environmental Protection Agency's next two deadlines for additional emissions restrictions on heavy-duty diesel engines. Diesels for fleet trucks such as USPS uses must meet tightened emissions standards in 2007 and even tighter rules in 2010. Redesigned engines to meet the rules are widely expected to make trucks cost more.