Purpose and Need

The interstate system in western South Dakota was built in the late 1950’s and early 1960’s and is approaching the end of its life expectancy. As I-90 is reconstructed, every effort must be made to bring it up to current design standards for safe travel. This will include widening the median in places, relocating the service roads to provide more separation from the interstate, and designing the roadways and interchanges so the mainline of I-90 may be expanded to three lanes in each direction in the future. The intent of this project is to provide safe local access via improved service roads, and to reconstruct I-90 to accommodate travel needs 40 to 50 years into the future.

Project Purpose and Objectives

To improve interstate operations, provide safe local access, and address future transportation demands throughout the corridor. Objectives within this overall project purpose are to:

• Increase spacing between substandard ramp terminal intersections and adjacent frontage roads and local access intersections
• Improve limited sight distances at ramp intersections and off-ramps due to horizontal and vertical curves, and bridge skew angles
• Correct inadequate tapers at the end of interstate on-ramps where merging vehicles enter high speed mainline traffic
• Increase safety along I-90 and on service roads by increasing distances between service roads and mainline I-90
• Improve future traffic operations along I-90, including the Exit 44 and Exit 46 interchanges, and along the service roads