Project Description

RPA was contracted to provide design services to implement a previous high-level planning study’s preferred configuration of roundabouts for the Rocker Interchange ramp terminals. Five- and six-legged roundabouts were developed to accommodate the interstate ramps, frontage roads, and business accesses in this tightly-constrained setting. Due to landowner opposition and political pressure, the south roundabout was converted to a standard intersection during design, implementing improved geometrics where feasible. The north roundabout includes outer truck aprons to accommodate the high volume of trucks, pedestrian amenities, and landscaping. Drainage is collected through the new storm drain system and retained on-site in a series of retention ponds. The plan sequence of operations allowed traffic to all roadways and businesses throughout construction.

Project Details​


Montana Department of Transportation


Rocker, Montana