SDCL § 31-27-18: Minimum overhead clearance--Width of roadway--Approaches.

The clearance or overhead room of any subway or undercrossing may not be less than fifteen feet from top of finished grade to bottom of sills of overhead track or trusses. The width or clear roadway of the subway or undercrossing may not be less than twenty-four feet, clear roadway. The approaches to the undercrossing or overhead crossing shall be straight and under no circumstances may these crossings contain curves.