About the Project

The South Dakota Department of Transportation (SDDOT) in conjunction with the City of Sioux Falls, the Sioux Falls Metropolitan Planning Organization (MPO) and the Federal Highway Administration (FHWA) has contracted with HDR Engineering, Inc. (HDR) to perform an interchange modification justification study for the I-29 Exit 77 interchange and conduct the associated environmental investigation.


As part of the I-29 Exit 77 (41st Street) Crossroad Corridor Study completed in 2012, it was determined that reconfiguring the I-29 Exit 77 (41st Street) interchange would be the best alternative to handle current and future traffic levels. At present, pending funding availability, the SDDOT intends to let for construction a project to reconfigure the Exit 77 interchange and the City of Sioux Falls intends on reconstructing and widening 41st Street from a point west of Marion Road to I-29 and reconstructing 41st Street from I-29 to a point west of Louise Avenue. This will also involve reconstruction of intersection legs north and south of 41st Street along the corridor, including Marion Road from 39th Street to 43rd Street. These projects are currently planned for Federal fiscal year 2021, which this interchange study will help bring to fruition.


The study will include performing a HCM 2010 based traffic analysis comparison of the reconfigured interchange options of the I-29 Exit 77 interchange brought forth by the I-29 Exit 77 (41st Street) Crossroad Corridor Study versus the existing configuration.


Study Objectives

  • Create an Interchange Modification Justification Report.

  • Conduct an Environmental Assessment.

  • Create final products for use by the City of Sioux Falls, the Sioux Falls MPO, and the SDDOT.

Interchange Options


Partial Cloverleaf Interchange Option



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Single Point Interchange Option



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Diverging Diamond Interchange Option



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