This project is part of a plan to improve the I-75 downtown Dayton subcorridor, a downtown urban interstate with complex horizontal and vertical geometrics, including complex bridges supporting I-75 mainline lanes and interchange ramps over city streets and railroads, serving about 140,000 vehicles per day. The total estimated construction cost for the improvement of the entire subcorridor is over $483 million. This phase of the project involves reconstructing and widening 1.33 miles of the south segment of the subcorridor. The project will construct three continuous mainline lanes in each direction through the US 35 and I-75 Interchange. This will modernize I-75 by establishing 3-lane continuity, removing geometric deficiencies, and updating entrance and exit ramps. Bridge work includes 18 new bridges, rehabilitation of an additional four bridges, and removal of three bridges. The scope of services for this project will include Steps 6 through 12 of the ODOT Project Development Process; roadway, bridge and retaining wall design; traffic control; drainage and BMPs; lighting; surveying; right-of-way plan design; a maintenance-of-traffic alternative analysis; aesthetics; a public information meeting; and design exceptions. The project will also involve close coordination with ODOT, District 7, the City of Dayton, Montgomery County, and the CSX and Norfolk Southern railroads.