Analyze each box culvert as a simply supported two-dimensional frame pinned at one support only and free to move horizontally at all other supports. Do not apply the edge beam requirement in Article 12.11.2.1.

For culverts with less than two feet of fill (i.e., "direct traffic"), distribute the weight of curbs and railing over the entire top slab width if the slab is no wider than 32 ft. Otherwise, distribute the curb and railing loads over 16 ft.