The short answer is yes: driving too slowly can break the law here, and the rule is more specific than most drivers realize. Driving 15 miles under the limit on a clear day with nowhere to pull over is the situation the law is actually aimed at. The Four-Car Rule: When Slow Drivers Must Pull Over in MontanaThe same statute lays out a specific trigger point. If the shoulder is wide enough and safe, the slow vehicle can move onto it and continue at a safe speed until it's passed. Left-Lane Passing Laws and Highway Traffic Rules in MontanaMontana requires passing to happen on the left in nearly all situations on a two-lane road.