If the depth of a box girder bridge exceeds 1/6 or 1/5 of the bridge width, then it is
recommended to be designed as a single cell box girder bridge. However, if the bridge
depth is smaller than 1/6 of the bridge width, then a twin-cell or multiple cell is a better
choice as suggested by Jorg Schlaich & Hartmut Scheef (1982). However, one should note that even for wider bridges with small depths, the number of cells should be minimized because there is not much improvement in transverse load distribution when the number of cells of box girder is increased to three or more.