The South Dakota Department of Transportation (SDDOT) and the Federal Highway Administration (FHWA) collaborated on a research study to determine the effects of a number of inlet geometry choices on culvert hydraulic efficiency. This study is a response to the large number of culverts that are installed in the United States and the fact that most of the current guidelines on culvert hydraulics are based on research completed more than 20 years ago. The objectives of this study were to: Determine optimum edge conditions for wingwalls; Determine the effects of inlet geometry on flow capacity of single and multiple barrel culverts with optimized edge treatment of wingwalls; Determine effects of the span-to-rise ratio on flow capacity with various inlet geometries; Determine the effects of skew on flow capacity of box culverts.