On motorway M6, starting southbound from the intersection of M6 and M9, the first bridge to be crossed is Sió Bridge located at the 144.9 km section. The structure is 240 meter long (consisting of 75, 90 and 75 m spans) 2×2 lane, bow-string type bridge, designed to carry the traffic of the expressway above the Sió Bridge. We decided to replace the twin-cell orthotropic carriageway concept specified in the tender design with an alternative approach using a composite structure approach, more specifically, the open box version.