The operator of a vehicle about to enter or cross a roadway from a private road, driveway, alley, or public approach ramp shall yield the right-of-way to all vehicles approaching on the roadway.
Vehicle Entering Roadway From Private Road, Driveway, Alley, Or Public Approach Ramp
Mont. Code Ann. § 61-8-343, under Vehicle Operating Requirements.
Mont. Code Ann. § 61-8-343