Montana Department of Transportation

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Gore Hill Interchange Project

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Project Overview

The Montana Department of Transportation is developing improvements to the Interstate 15 (I 15) Gore Hill Interchange (EXIT 277) in Great Falls. The Gore Hill Interchange provides access to the Great Falls International Airport as well as the surrounding residential, commercial and industrial developments. The project will reduce delays, and improve traffic flow and safety on I 15 between 10th Ave. South and the Gore Hill Interchange.

project map
Gore Hill Interchange project map

Project Background

In 2015, the Montana Department of Transportation (MDT) developed the I-15 Gore Hill to Emerson Junction Corridor Planning Study in partnership with the Federal Highway Administration and the Great Falls Metropolitan Planning Organization. The study identified safety and operational concerns, and recommended improvement options to address the transportation needs within the corridor through 2035. Among these improvement options were the addition of a southbound auxiliary lane between the Gore Hill and 10th Avenue South interchanges, and intersection improvements at the Gore Hill Interchange.

The Great Falls Long Range Transportation Plan (LRTP) 2018 Update also included recommendations to make improvements to the Gore Hill Interchange as outlined in the Corridor Planning Study.

The 2015 I 15 Gore Hill to Emerson Junction Corridor Planning Study and 2018 Great Falls Long Range Transportation Plan identified several safety and operational concerns at the Gore Hill Interchange. Transportation issues and concerns included:

  • Congestion and safety concerns due to high traffic volumes, especially during peak hours, and close intersection spacing.
  • Limitations in current intersection designs to handle increasing airport, truck stop and other commercial truck traffic volumes.
  • Merging conflicts with truck traffic on I 15 due to the short distance between the 10th Avenue South Interchange and the Gore Hill Interchange.
Gore Hill Interchange area in Great Falls, MT

Planned Improvements

New Interchange Design for the Gore Hill Interchange
New Interchange Design - Click to view a larger image.
  • The I 15 Gore Hill Interchange overpass bridge will be replaced. The new structure will be built to the east of the current overpass to keep the interchange open during construction. The new bridge will be wider and include 12-foot travel lanes, 8-foot shoulders and a sidewalk.
  • Two single-lane roundabouts will be added on 31st Street SW at the I 15 southbound off-ramp and northbound on- and off-ramps. A sidewalk will be added between the roundabout intersections.
  • An additional southbound lane will be added to I 15 between the 10th Avenue South and Gore Hill interchanges. The lane will exit on to the southbound Gore Hill Interchange off-ramp.
  • The Tri Hill Frontage Road and 31st Street SW intersection will be relocated to the south.

The new bridge design and roundabouts will accommodate over-sized trucks through the intersections.

Why a roundabout?

MDT considered several improvement options for the intersections including traffic signals. After evaluation, MDT determined that a roundabout is the safest way to efficiently control traffic at the intersections. Roundabouts have been shown to improve efficiency and provide a smoother traffic flow including an 89% reduction in delays and 56% reduction in stops.

Roundabouts have a number of other safety benefits including:

  • Increased safety due to a reduction of conflict points and a reduced speed throughout the intersection.
  • A 90% reduction in fatal collisions when compared to stoplights or stop signs.
  • A 40% reduction in pedestrian collisions.

View More Information about Roundabouts

Project Process and Tentative Schedule

I 15 Gore Hill to Emerson Junction Corridor Planning Study identified issues and concerns 2015
Great Falls Long Range Transportation Plan recommends improvement options to evaluate 2018
Potential alternatives evaluated and improvements developed 2018-2019
Recommended improvements presented to the public 2019
Detailed plans for new interchange design developed 2020
Preferred alternative presented to the public 2020
Final design presented to the public 2021

UPN 9345000