How do I get an accident report in Montana?

You have to make a request to the relevant department or governmental agency. Usually in the context of a trucking or case accident this will be the police, sheriff or the highway patrol. 

The following persons can request a report: 

(a) a person named in the report or involved in the accident;

(b) the representative of the person referred to in subsection (2)(a), designated in writing, or the insurance carrier of that person;

(c) a party to a civil action arising from the accident;

(d) the executor, the administrator, or the attorney representing the executor or administrator if the person is deceased; or

(e) the general public, including commercial entities, for purposes of research into the history of vehicles, but the department may not disclose the name, address, or telephone number of, or other information allowing the identification of, any reporting person, accident victim, peace officer, or other person or any insurer named in a report or supplemental information, including witness statements.

See 61-7-114, MCA and