The I-90 & LaCrosse Street DDI is in its final stage of construction and will be operational in the summer of 2023.

About the Project

The I-90 & LaCrosse Street Interchange Project (Exit 59) on Interstate 90 will help improve safety, road conditions, and future travel needs and growth. These issues were included as part of the 2010 South Dakota Decennial Interstate Corridor Study and the Rapid City Area Metropolitan Planning Organization 2015 Long-Range Transportation Plan.

The South Dakota Department of Transportation (SDDOT) completed an Interchange Modification Justification Report (IMJR) that evaluated potential changes to help ease current and future capacity issues. Traffic volumes for North LaCrosse Street are projected to increase by 35 to 65 percent by the year 2035. In addition, several turning movements at the interchange are expected to reach high delay levels. The solutions considered in the IMJR continue to promote a livable community that enhances the economic and social well-being of Rapid City residents and visitors.

The Solution

The interchange modification will reduce current delay and traffic issues for motorists by increasing the capacity and extending turn-lanes at the interchange. The project team looked at a variety of things during the interchange design, including the ability to handle traffic demands, constructability, environmental concerns, landowner impacts, and public input. The Diverging Diamond Interchange (DDI) configuration was selected to meet the purpose and need for the project. The IMJR was approved by Federal Highway Administration on April 9, 2015.

What is a Diverging Diamond Interchange?

Watch this video to see how a Diverging Diamond Interchange works


Project Elements

The proposed project includes reconfiguration of the existing diamond interchange into a Diverging Diamond Interchange (DDI) with the associated project elements: