in profile. Variations include the Baltimore truss and Pennsylvania truss. Elaboration in the form of variable depth from sloping upper chords as in the Camel-back arrangement, reduced the amount of steel required, and also dead weight for a similar strength. The Pratt truss compares to Warren truss and Howe designs in the different compression and tension arrangements of diagonal and vertical members. It was named for Thomas W. and Caleb Pratt (Boston railway engineers), who were issued a patent for a truss bearing their name in April 1844. The overall length is given in VicRoads inventory as although a deck length of and total length of in their inspection system appears more probable. The nine truss spans are each with the NSW approach span being ; clear height is and width . Concrete endposts frame the entry to the bridge. The construction date is cast in the one end post. The original wooden road surface has been raised once and twice replaced, the railings replaced and the NSW approach modified. Nevertheless, Bethanga Bridge remains substantially the same structure erected in the 1920s. Heritage listing Bethanga Bridge was built between 1927 and 1930 as a joint venture between New South Wales and Victoria as part of the Hume Dam project as a key element of the River Murray Waters Agreement put in place in 1915 by the Victorian, New South Wales, South Australian and Federal governments to regulate the flow of the Murray River as a provision against drought and to ensure that the three states received their agreed share of water. The use of Pratt trusses is unusual in Victoria, not being readily taken up as a viable bridge design. However they are more common in New South Wales. The use of the Pratt truss in this instance reflects the mode of construction employed during the construction of the Hume Dam whereby the New South Wales Department of Public Works and the Victorian State Rivers and Water Supply Commission were jointly responsible for the design and construction of the bridge. The bridge was designed in New South Wales by Department of Main Roads engineer Percy Allen and the trusses were built by Vickers Ruwolt in Melbourne. The Murray River boundary between New South Wales and Victoria is the top of the southern bank of the river. As such all structures of the river are considered to be in New South