Rapid City Major Investment Study

Over the past two decades, the SDDOT has addressed issues at individual interchanges—exit 51 (diamond, 2010), exit 55 (tight diamond), exit 58 (SPUI, 2001), exit 59 (Divided Diamond, 2023), exit 60 (SPUI, 2007), and exit 61 (SPUI)—but these piecemeal fixes weren’t evaluated for their corridor‑wide effects across I‑90 and US‑16B. With continued growth and evolving travel patterns, the region now needs a coordinated, system‑level plan that analyzes how the two corridors work together, pinpoints safety and capacity needs, and tests feasible, cost‑conscious solutions for 2035, 2045, and 2060. The study will also clarify the future role of US‑16B (e.g., highway vs. urban arterial), integrate origin–destination and incident/ITS insights, and prepare an Environmental Screening to streamline future NEPA steps—ensuring improvements deliver benefits across the entire network.

Over the past two decades, SDDOT, the City of Rapid City, the RC MPO, and FHWA have advanced targeted interchange upgrades along I‑90—e.g., exits 55, 58, 59, 60, and 61—while the US‑16 Bypass has been defined from the US‑16 split at Catron Boulevard to I‑90 at exit 61. This Major Investment Study builds on that work by evaluating I‑90 (MRM 52–62) and US‑16B together as an integrated system, using prior studies and RC MPO plans to frame analyses of 2025 existing and 2035/2045/2060 future conditions. It will also determine the future categorization of US‑16B and prepare an Environmental Screening to connect planning recommendations to subsequent NEPA steps and long‑term corridor development.

This study covers two connected corridors in Pennington County, serving Rapid City and Black Hawk, with analysis generally within a half‑mile buffer around the corridors.

Corridor extents

• I‑90: From exit 52 (Peaceful Pines Road/S.D. Highway 231) to exit 61 (US‑16 Bypass), eastbound and westbound (≈ 9.5 miles; MRM 52.00–62.00).

• US‑16 Bypass (Catron Boulevard/Elk Vale Road): From the US‑16 split at Catron Blvd to I‑90 at exit 61 (≈ 9 miles), plus short analysis segments on Catron Boulevard (≈ 1,400 ft) and Elk Vale Boulevard (≈ 1,500 ft) for system continuity.

Roadway elements included

• I‑90 interchanges: exit 52 (Peaceful Pines/S.D. Highway 231), 55 (Deadwood Avenue/S.D. Highway  445), 57 (I‑190/US‑16), 58 (Haines Avenue), 59 (La Crosse Street), 60 (Tish Boulevard/E. North Street/I‑90 Bypass), 61 (US‑16 Bypass/Elk Vale Road).

US‑16 Bypass key junctions: S.D. Highway 79/Cambell Street interchange; S.D. Highway 44 interchange (NB/SB ramp terminals); Eglin Street/Cheyenne Boulevard; Elk Vale Road & East Mall Drive; Black Hills Boulevard; 5th Street. (Additional intersections are analyzed per the full study list.)

Studies follow a phased process that typically includes project initiation, data collection, analysis of existing and future conditions, public meetings, development and evaluation of improvement alternatives, and preparation of final study recommendations. Key milestones may include coordination with stakeholders, opportunities for public input, and release of final materials. This study is expected to run from September 2025 to the end of June 2028.

Document how the public is/will be informed, how they can participate, and provide access to meeting materials and engagement activities. Reference federal requirements, the SDDOT’s Public Involvement Plan. All public meeting materials will go through a review process, with the SAT, the communications team, and Governor’s office. Once reviewed and approved, all applicable meeting materials will be provided to the communications team (ADA compliant) for upload to the SDDOT website for public access.

Public Meeting #1, Dahl Arts Center at 5:30 p.m. (MT)

• Flyer

• Presentation

• Recorded Presentation

• Displays

The study advisory team is comprised of representatives from the SDDOT, the Rapid City Metropolitan Planning Organization, the City of Rapid City, Ellis Air Force Base, Box Elder, Pennington County, and the Federal Highway Administration.