The 2009 interim contains replacement pages for the AASHTO LRFD Bridge Design Specifications, 4th Edition, Customary U.S. Units, 2007. There is no 2009 SI Interim as per a decision made by the AASHTO Highway Subcommittee on Bridges and Structures. The 2009 U.S. Interim is necessary to have all current specification information. CD-ROM is included with purchase of "Looseleaf/CD" format