Montana Department of Transportation

Malcolm “Mack” Long, Director


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Rocker Interchange Rocker Interchange Rocker Interchange Rocker Interchange Rocker Interchange

Public Involvement

Rocker Interchange  project logo

Rocker Interchange

Project Overview

The Montana Department of Transportation is continuing construction activities in Rocker, Montana at the intersections of Interstates 90 and 15 to modernize and finalize efforts on nearby intersections, ramps, and frontage roads.

The project began in the Spring of 2019 and will continue through the 2020 construction seasion.


The Rocker Interchange Project is an effort at providing safe, modern roadways and improvements to one of Montana’s largest interstate interchanges. Improvements will specifically include:

  • Improving and modernizing ramps to better accommodate large trucks;
  • Replacing a complicated five-legged intersection with a less-confusing modern roundabout;
  • Improving traffic flow and drivability in the intersection; and
  • Improving frontage roads to make them more pedestrian friendly.

These improvements were selected to increase ease of use and traffic flow in an area with high volumes of commercial and private vehicle traffic. Improvements will meet current state and federal standards of safety, cost-effectiveness, and efficiency, providing benefits to travelers and the surrounding community.

Timeline and Budget

The project began in the spring of 2019 and will conclude in 2020. The budget for this project is just over $6 million dollars.


Truck Traffic

Roundabouts are constructed with large trucks, RVs, equipment, and horse trailers in mind. The interior section of the roundabout containing colored and patterned concrete is called a truck apron and vehicles are encouraged to use the truck apron to be able to safely drive through the roundabout.

Mountable Truck Apron

  • Trucks can track onto mountable apron.
  • Designed with flat slope and low height to accommodate low clearance vehicles.
  • Sufficient width for trailer turning paths.

Large Loads

  • Designed to accommodate the turning movements of large trucks.
  • Roundabout design and size influenced by truck turning paths.

Multi-lane Design

  • Large trucks can use both lanes if needed.
  • Provides additional space for large loads.

Below is a video illustrating the use and success of truck aprons.

Traffic Flow

High volume areas of traffic, like the Rocker Interchange, require the use of most effective solutions MDT has to keep Montanans moving on our roads.

Roundabouts provide improved safety and traffic flow by reducing the number of collision points that happen at tradition intersections, like the one currently at the interchange. Fewer collision points mean safer crossing for vehicles and pedestrians.