An overview of Montana's bicycle laws, reviewed and cited to primary sources. Use the sections below to jump to a specific rule, or the Sources block at the end for the full citation list.
This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
Helmet rules
Required under age
No statewide age requirement
Applies to passengers
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Standard
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Penalty
Montana has no statewide bicycle helmet law for any age, and no Montana municipality currently requires helmets for general bicycle use. Federal CPSC certification (16 CFR Part 1203) applies to every helmet sold in the state.
MCA § 61-8-607 grants a person riding a bicycle on a sidewalk all the rights and duties applicable to a pedestrian under the same circumstances; the rider must yield to pedestrians and give an audible signal before overtaking. Local authorities may prohibit sidewalk riding by ordinance — Missoula and Bozeman both restrict it in their downtown business districts.
Montana's DUI statute (MCA § 61-8-1002) applies to anyone in actual physical control of a 'vehicle' on a way of the state open to the public. MCA § 61-1-101 separately defines 'bicycle' and excludes human-powered devices from the operative definition of 'motor vehicle' for DUI purposes; in practice Montana law enforcement does not charge cyclists with DUI. Open-container and disorderly-conduct charges remain available.
Lamp on the front emitting a white light visible from a distance of at least 500 feet to the front, required during darkness or whenever low visibility makes it difficult to identify persons and vehicles at 500 feet.
Rear requirement
Rear reflector or light
Rear spec
Red reflector on the rear of a type approved by the Montana Department of Justice, visible from all distances from 100 feet to 600 feet when directly in front of lawful lower-beam headlamps. A red rear lamp visible from 500 feet may be used in addition to the reflector.
Two abreast permitted on the roadway except on parts of roadways set aside for the exclusive use of bicycles, where the cap does not apply. Riders shall not impede the normal and reasonable movement of traffic and shall move to single file when overtaken on narrow roadways.
Bicycles are permitted on Montana Interstate shoulders where no reasonable alternative route exists, under MDT bicycle policy. I-15, I-90, and I-94 are open to bicycles across most of their rural Montana mileage; specific tunnels, urban segments (Billings, Missoula, Bozeman), and bridges may be signed prohibited. Always check the on-ramp signage and the MDT Bicycle and Pedestrian Program map before entering.