This code covers the welding requirements for AASHTO welded highway bridges made from carbon and low-alloy constructional steels. This 2008 edition contains dimensions in metric SI Units and U.S. Customary Units. Clauses 1 through 7 constitute a body of rules for the regulation of welding in steel construction. The provisions for Clause 9 have been distributed throughout the D1.5 code. Clauses 8, 10, and 11 do not contain provisions, as their analogue D1.1 sections are not applicable to the D1.5 code. Clause 12 contains the requirements for fabricating fracture critical members. The code is not intended to be used for the following: (1) Steels with a minimum specified yield strength greater than 690 MPa [100 ksi] (2) Pressure vessels or pressure piping (3) Base metals other than carbon or low alloy steels (4) Structures composed of structural tubing