To speed construction, the elevated trackway is built using precast concrete box girder bridge segments. Instead, there is a mix of more modest girder, truss and cable bridges. The Middle Arm Bridge is a shorter box girder bridge. SPSW behavior is analogous to a vertical plate girder cantilevered from its base. Its behaviour is analogous to a vertical plate girder cantilevered from its base. Its behavior is analogous to a vertical plate girder cantilevered from its base. The overpasses along the road consisted of steel girder bridges and through plate girder bridges. Two additional spans of length would complete the bridge, making a continuous girder. These can be built using typical steel beams or a more complex box girder type. Its fuselage was a rectangular section girder, covered with plywood sheets. This was in turn replaced in 1904 by a steel girder bridge. The first girder for the new bridge was installed in February 1909. Later work was applied to bridge building, and the invention of the box girder. The two most common types of modern steel girder bridges are plate and box. Block rail is a lower profile form of girder guard rail with the web eliminated.