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Project Overview

In conjunction with Riverside Contracting, this spring and summer, the Montana Department of Transportation (MDT) will continue construction of Phase 3 of the Belt N & S project at Armington Junction, which is the intersection of US Highway 87 (US 87) and US Highway 89 (US 89) near Belt

This project will:

  • Reconstruct approximately 3.5 miles of existing US 87, including widening the roadway to five lanes starting after the Belt Creek bridge in the westbound direction towards Belt and Great Falls.
  • Construct a roundabout at Armington Junction.
  • Construct a new bridge over Belt Creek, a new culvert over Neil Creek, and a new culvert at Frenchman’s Coulee.
Armington Junction Roundabout Project map

Click to view a larger image.

Construction Impacts

Construction is scheduled to begin in mid-April and be substantially complete by mid-summer. The traveling public should expect 15-minute delays, flaggers, temporary stoplights, and pilot cars.

Why Armington Junction?

Armington Junction is not only the intersection of two major highways, US 87 and US 89; it is also the entrance to a rest area and weigh station that creates additional conflict points, is confusing to motorists, and is a significant safety concern.

The current T intersection at Armington Junction, plus the weigh station and rest area, create 28 conflict points for potential crashes. A single-lane roundabout would reduce those conflict points to eight, therefore enhancing roadway safety features. After studying four alternatives and consulting with the public and critical stakeholders, MDT has determined a roundabout is the safest option.

Crashes at rural intersections often are at high speeds, resulting in severe injuries or fatalities. Approximately 1/3 of annual intersection fatalities in the United States occur along rural, two-lane highways.

Because of the severity of crashes, a crash history analysis performed during the design phase of the Armington Junction project for ten years reported nine crashes, including one fatality. More recently, news reports documented an additional three-fatality crash in 2013 and a four-fatality crash in 2019 near Armington Junction. This pattern must stop. MDT is committed to creating a solution that eliminates serious injuries and deaths at this intersection.


- Naturally eliminate the deadliest T-bone style crashes through their circular shape and one-directional traffic flow.

- Make things easier on drivers by removing the most problematic cross-traffic and left-hand turning maneuvers.

- Allow drivers to simply slow down, look to their left, and gently merge into the roundabout before traveling around the circle to their destination.

But do not take our word for it. Listen to what Montana Highway Patrol Trooper Brian Inman has to say about how roundabouts improve the safety of intersections.

Designed to Accommodate Large Trucks

The Armington Junction Roundabout will be the largest single-lane roundabout in Montana. The large size of the Armington Junction roundabout will ensure that it will accommodate various large, oversize, and overweight vehicles, including trucks carrying wind farm blades and US Air Force munition haulers.

The interior section of the roundabout containing patterned concrete is called the ‘truck apron.’ Its purpose is to accommodate the wheels of trucks and long vehicles to travel through the roundabout safely. The truck apron is specially designed with a flat slope and low height to accommodate low-clearance vehicles and trailers.

This video shows how a truck apron works.

For this project, our engineering partner, Jacobs, ran computer simulations with various large and oversized trucks to ensure that this roundabout would accommodate the type of vehicles that use US 87 and US 89. Watch the simulations here.

Project Timeline

Construction began in August 2021 and will likely be substantially complete by mid-summer 2023.

Project Costs

The cost of the intersection improvements, including the widening of existing roads to meet safety and design standards, the construction of the roundabout, and the bridge and culvert replacements, is approximately $19.4 million.

Roundabouts not only save lives but money too. The Canyon Ferry and Lake Helena Drive roundabout reduced crashes by 70% and eliminated fatalities over five years. The six-year cost savings of installing that roundabout was nearly $6 million.

Armington Canyon Ferry Case Study

Click to view a larger image.

The Armington Junction Project is funded through the National Highway System (NH) Program, which finances highway and bridge projects to rehabilitate, restore, resurface, and reconstruct non-Interstate National Highway System routes. Montana’s Transportation Commission allocates the five Districts for MDT NH funds based on system performance, and the Great Falls District has utilized its allocation to fund this project.

Slow For The Cone Zone

When traveling during construction season, watch for the “cone zone” and workers on the highway. These workers spend their days working a short distance from fast-moving vehicles, and while they make every effort to work safely, they count on you to pay attention, slow down and be careful as you pass through a work zone.

Stay in the Know

You can receive detailed updates about when construction will occur and what the impacts will be through the following:

Email melissasXYZstrategies360ABCcom
Text "belt" to 406-226-1603*
Call public involvement lead Melissa Shannon at 406-422-2922

*Texting alerts are not managed by MDT and may have different privacy and security policies. For more information read the SimpleTexting Privacy Policy.

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