Quick answer
According to crimebycity.com's analysis of NHTSA data, the most dangerous city to drive in in Montana is Billings, MT with 9.5 traffic deaths per 100,000 residents per year (2020–2024; Road Danger Score 61/100), vs a US average of 12.3.
Highest Traffic-Fatality Rates in Montana
Cities ranked by Road Danger Score — 5-year traffic deaths per 100,000 residents from NHTSA FARS.