Old U.S. Highway 14 and Interstate 90 (Exit 10)

Project Overview:

The South Dakota Department of Transportation (SDDOT) is improving the intersection of U.S. Highway 85 (North Avenue), Old Highway 14, and the I-90 Exit 10 eastbound ramps in Spearfish.

A 2024 traffic study identified safety concerns and traffic challenges in this area, particularly due to the closely spaced intersections. Based on this analysis, a Reduced Conflict Intersection (RCI) was selected to improve safety and traffic flow while still allowing for future interchange improvements.

The design is intended to reduce the risk of severe crashes and support traffic growth through approximately 2038.

Reduced Conflict Intersection (RCI) Information:

The selected design includes an RCI at the intersection of North Avenue and Old Highway 14.

This design changes how certain turning movements occur to reduce conflict points and improve safety. At this location:

• Left turns from Old Highway 14 to northbound North Avenue will be redirected using a median U-turn located south of the intersection

• Through movements on North Avenue will continue as they do today

The updated intersection is designed to accommodate all types of vehicles, including large trucks and trailers.

Construction Updates:

June 15, 2026: 

Beginning Monday, June 22, 2026, crews will begin work on the intersection improvements and lighting for the Spearfish (exit 10) reconstruction project on Interstate 90. During the first stage of construction, North Avenue will be reduced to one lane in each direction as crews remove old pavement and begin constructing the new “Loon” left turn feature. The I 90 on-ramps and off-ramps will remain open throughout the project.

Later in the summer when construction of the median begins, left turns from Old Highway 14 will be prohibited. This reconstruction project includes modifying the exit 10 intersection and adding new traffic signals and luminaires. Drivers should plan for slower speeds and stay alert for changing traffic patterns throughout the work zone.

Informational Meeting Reminder:

On Thursday, June 18, 2026, the SDDOT in collaboration with the project contractor, Tru-Form Construction, Inc., will hold an informational meeting to discuss the upcoming reconstruction project at Spearfish (exit 10) on Interstate 90. The informational meeting, which will include construction timelines and traffic changes, is scheduled to begin at 5 p.m. in the large conference room at Hudson Hall, located at 222 W. Hudson St. in Spearfish.

The informational meeting is designed to share overall construction project details, traffic flow, and to answer questions for members of the public including impacted residents, local businesses, and emergency service personnel. The meeting will be informal, with opportunities for one on one conversations with SDDOT engineering staff.

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Construction will include the following:

• Install a median to limit certain left turns at the North Avenue and Old Highway 14 intersection

• Install a median U-turn south of the intersection to support redirected movements

• Add a northbound right-turn lane at the I-90 eastbound ramp intersection

• Resurface pavement and make general roadway improvements

• Update signs, pavement markings, and traffic control

Future Intersection Layout:

STATEWIDE CONSTRUCTION PROJECTS PAGE

PCN: 08LL