Under Montana's lane-filtering law (MCA 61-8-392), a motorcyclist may pass between lanes of stopped or slow traffic only when:

1. The motorcycle is going up to 50 mph
2. The motorcycle is at or below 20 mph, the vehicles being passed are stopped or moving at 10 mph or less, and the lane is wide enough to pass safely
3. Traffic is moving at any speed and conditions are clear
4. It is dark and traffic is light