Montana Department of Transportation

Roadway Departure Study


The following items are prepared solely for the purpose of identifying, evaluating and planning safety improvements on public roads in Montana. It is subject to the provisions of 23 U.S.C. 409, and therefore is not subject to discovery or release through Public Information Requests and is excluded from admission into evidence. Applicable provisions of 23 U.S.C. 409 are cited below:

Notwithstanding any other provision of law, reports, surveys, schedules, lists, or data compiled or collected for the purpose of identifying, evaluating, or planning the safety enhancement of potential accident sites, hazardous roadway conditions, or railway-highway crossings, pursuant to sections 130, 144, and 152 of this title or for the purpose of developing any highway safety construction improvement project which may be implemented utilizing Federal-aid highway funds Shall not be subject to discovery or admitted into evidence in a Federal or State court proceeding or considered for other purposes in any action for damages arising from any occurrence at a location mentioned or addressed in such reports, surveys, schedules, lists or data.

Any intentional or inadvertent release of this report, or any data derived from its use shall not constitute a waiver of privilege pursuant to 23 U.S.C. 409.

Roadway departure crashes occur when a vehicle leaves the travel lane, either crossing into an opposing lane, or leaving the roadway. These crashes often occur at high speeds so are likely to be severe. The crash may include impact with an object on the side of the road, a vehicle in an opposing lane, or overturning.

Almost all, 96 percent, of roadway departure fatalities and serious injuries occur in rural areas, making this type of severe crash the most common in Montana during the time period of 2004 to 2013. These crashes accounted for 67 percent of all fatalities and 55 percent of serious injuries.

In an effort to address this crash type, MDT developed a Road Departure Study for rural, on-system routes. The results of this study are being used to identify locations for potential engineering improvements to address crash trends. A link to the summary of the analysis is provided below. Detailed reports outlining the development of the study and maps depicting the Level of Service of Safety (LOSS) for evaluated locations and identified crash patterns are also provided in the following links.

Crash data used for the analysis is from the Montana Department of Transportation (MDT) Safety Information Management System between January 1, 2008 and December 31, 2012.


Tricia Burke
406-444-9420 |