US 191 Corridor Study Four Corners to Beaver Creek logo

What is a Corridor Study?

A corridor study is a planning-level assessment occurring before project-level activities and environmental compliance under the National and Montana Environmental Policy Acts (NEPA/MEPA). This process provides a link between early transportation planning and environmental compliance efforts, and involves a planning–level evaluation of safety, operational, and environmental conditions to identify needs and constraints.

MDT can save time and money in subsequent project phases by facilitating early identification of constraints through coordination with local governments, resource agencies, and other stakeholders; screening of possible improvement options; and elimination of infeasible options.

A planning study considers multiple improvement options to address the needs and objectives within a study area. The planning process is distinct from a NEPA/MEPA environmental compliance document and from design, right-of-way acquisition, and construction phases for an individual project.

For additional information, please see MDT's planning study process.

What does a "pre-NEPA/MEPA planning study" mean?

The National and Montana Environmental Policy Acts (NEPA/MEPA) require state and federal agencies to disclose impacts resulting from state and federal actions. In the context of transportation projects, the NEPA/MEPA process is intended to assist officials in making transportation decisions, while considering the human and natural environment and the need for a safe and efficient transportation network. The NEPA/MEPA process ensures that information about anticipated transportation project impacts is available to the public before decisions are made and executed.

A corridor study is a pre-NEPA/MEPA effort that involves a planning-level assessment of the study area. The planning process includes a review of potential environmental issues and concerns. The results of this planning-level environmental review could be used to assist in later NEPA/MEPA environmental compliance phases for an individual project.

Who conducted this study?

The Montana Department of Transportation conducted this study in partnership with the Federal Highway Administration (FHWA) and in coordination with Gallatin County. Robert Peccia and Associates (RPA) assisted MDT in completing the planning effort.

What happens after the study?

The corridor study identified and evaluated potential improvement options for the study corridor. This early planning process is distinct from the environmental compliance, design, and construction phases of an individual project. Any future steps will be determined by MDT in conjunction with FHWA and Gallatin County.

How was the public involved in the study?

Members of the public were encouraged to participate in the planning process. Two public informational meetings were held during the corridor study process. The first set of meetings were held in January 2020 at two locations: one in the Big Sky area and one in the Four Corners/Gallatin Gateway area. Due to health and safety restrictions, the second set of meetings were held virtually in July 2020. Members of the public were invited to review information posted to the study website and provide input. Responses to public comments received during the public review period from July 22 through August 28, 2020, are provided in Appendix 1 of the final Corridor Study Report.