Westgate Bridge is the largest bridge in Melbourne. The main span over the Yarra river is 336m long and made of a cable stayed steel box girder whereas the approaches are made of prestressed concrete multicell box girder. Western viaduct consists of 10 spans at 67m each and the Eastern Viaduct consists of 13 spans at 67m each. The traffic loading is to be increased by converting the outer shoulders into typical traffic lanes. Accordingly, the entire bridge is to be strengthened to enhance its structural capacity. The Western viaduct has already been partly strengthened in 2002. Strengthening is made of carbon fiber strips outside of the box girder, and additional external prestressing inside the box girder.