The document describes the Do Vang bridge, which is part of a railway line bridges safety improvement project in Vietnam. The Do Vang bridge crosses the Rao Nay River and has 4 prestressed concrete spans and 2 steel truss spans, for a total length of 230.4 meters. The natural conditions of the bridge construction area include hilly terrain, seasonal rainfall and winds, and geological layers consisting of poorly plastic clay and weathered granite. The project scope involves designing and constructing the bridge using reinforced concrete, prestressed concrete, and steel trusses according to applicable Vietnamese standards.