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

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