Motorcycle helmet and lane-filtering laws in Montana

Montana runs its own playbook for two-wheeled riders. Adults here can legally ride bareheaded, and since 2021 the state has allowed a narrow form of lane filtering that most of the country still bans outright. If you ride, or you were just hit while riding, the exact wording of these two laws matters. It shapes what you can be ticketed for and, after a crash, what an insurer will argue about your injuries.

Here is what Montana law actually says.

Montana's helmet law covers only riders under 18

Montana's helmet rule is narrow. Under Mont. Code Ann. 61-9-417, only an operator or passenger under 18 years old on a motorcycle, moped, motorized scooter, or quadricycle has to wear protective headgear, and that headgear has to meet standards set by the state Department of Justice.¹ One carve-out exists: the rule doesn't apply inside an autocycle with a fully enclosed cabin, meaning a windshield, non-removable doors, and a roof.¹

For anyone 18 and older, the helmet is a personal choice rather than a legal duty. Montana is one of a small group of states with a partial law instead of a universal one. The statute governs headgear only. It sets no eye-protection or face-shield requirement.¹

The passenger clause is easy to miss. If you carry a rider under 18, the law puts a helmet on them regardless of your own choice, and the ticket is yours if they go without.

That freedom carries real risk. The Montana Department of Transportation reports that in a crash, an unhelmeted rider is 40 percent more likely to suffer a fatal head injury than a helmeted one.² The federal numbers point the same way: NHTSA estimates helmets are about 37 percent effective at preventing death for riders and 41 percent for passengers.³

What Montana's lane-filtering law actually allows

People throw around "lane splitting" loosely, but Montana law draws a hard line, and only one side of it is legal.

Since October 1, 2021, Mont. Code Ann. 61-8-392 has allowed lane filtering by two-wheeled motorcycles.⁴ Montana became the third state to permit it after the Legislature passed Senate Bill 9 during the 2021 session.⁵ The statute defines filtering as overtaking and passing a vehicle that is stopped, or moving no faster than 10 miles an hour, in the same lane and the same direction of travel.⁴

The conditions are specific. You may filter only when the road has lanes wide enough to pass safely, your motorcycle is traveling no more than 20 miles an hour while overtaking, and conditions allow reasonable and prudent operation of the bike.⁴

The numbers do the work here. The vehicle you pass has to be stopped or crawling at 10 mph or less, and you can't top 20 mph as you go by. Filtering up the gap between two lanes of moving highway traffic, the picture most people carry of "lane splitting," is not what this statute permits. A rider threading traffic at 40 mph while cars roll along at 35 is operating outside 61-8-392, which means a ticket, and in a collision, a share of the blame. The law also doesn't cover passing on the shoulder or squeezing past traffic that's moving faster than a crawl. Both stay illegal.

Why skipping a helmet can still cost you

Here's the part many riders get wrong. Because Montana doesn't require adults to wear helmets, some assume helmet use can never be held against them after a wreck. It can.

Montana follows modified comparative negligence. Under Mont. Code Ann. 27-1-702, you can recover damages as long as your share of the fault is not greater than the other side's, and your award drops by your own percentage of fault.⁶ Once your fault crosses 51 percent, you recover nothing.

Seatbelts get a special shield against this kind of argument. Mont. Code Ann. 61-13-106 says a person's failure to buckle up isn't admissible in a civil injury case and doesn't count as negligence.⁷ But that shield is tied to the seatbelt statute, 61-13-103, and that statute expressly exempts motorcycle operators.⁸ There is no matching helmet rule. So when an adult rider takes a head injury while unhelmeted, the defense can argue that part of that specific harm was avoidable and ask the jury to trim the head-injury damages. It doesn't move blame for the crash itself. What it can do is shrink the recovery for injuries a helmet might have softened.

Riding legal and riding protected are two different questions in Montana.

Deadlines, insurance, and the crash report

Montana gives you 3 years from the date of the crash to file a personal-injury lawsuit under Mont. Code Ann. 27-2-204, and 2 years for damage to your motorcycle or gear under 27-2-207.⁹¹⁰ Blow past those deadlines and the claim is almost always dead, no matter how serious the injury.

Montana is an at-fault (tort) state with no personal injury protection. Every driver has to carry at least 25/50/20 liability coverage: $25,000 per person and $50,000 per crash for bodily injury, plus $20,000 for property damage, under Mont. Code Ann. 61-6-103.¹¹ Those limits run thin fast in a serious motorcycle wreck, which is why your own uninsured and underinsured motorist coverage can matter more than the other driver's policy. Montana insurers have to offer UM/UIM matching your liability limits unless you rejected it in writing (Mont. Code Ann. 33-23-201).¹² Pull your own declarations page and check, because that coverage may be what pays your medical bills.

A couple of practical steps after a Montana motorcycle crash. Get the official report, which the Montana Highway Patrol keeps and releases through its crash-records process; you can start that at Montana crash reports. If your bike was totaled or lost value even after a clean repair, that's a separate diminished value claim in Montana. And when injuries are significant or the other side is fighting fault, it's worth talking to a lawyer; you can find one through the legal directory.

Montana gives riders more freedom than almost any other state. It also puts more of the consequences on the rider. Knowing exactly where the lines sit, on your head and in the lane, is what protects both your safety and your claim.

This article is general information, not legal advice.

Sources

1. Montana Code Annotated 61-9-417, Protective headgear required. https://mca.legmt.gov/bills/mca/title_0610/chapter_0090/part_0040/section_0170/0610-0090-0040-0170.html

2. Montana Department of Transportation, Vision Zero, Motorcycle Safety. https://mdt.mt.gov/visionzero/people/motorcycles.aspx

3. NHTSA, Traffic Safety Facts: Motorcycles (2023 data). https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813732.pdf

4. Montana Code Annotated 61-8-392, Lane filtering for motorcycles. https://mca.legmt.gov/bills/mca/title_0610/chapter_0080/part_0030/section_0920/0610-0080-0030-0920.html

5. Montana Senate Bill 9 (2021 Regular Session), bill status. https://legiscan.com/MT/bill/SB9/2021

6. Montana Code Annotated 27-1-702, Comparative negligence. https://mca.legmt.gov/bills/mca/title_0270/chapter_0010/part_0070/section_0020/0270-0010-0070-0020.html

7. Montana Code Annotated 61-13-106, Evidence not admissible. https://mca.legmt.gov/bills/mca/title_0610/chapter_0130/part_0010/section_0060/0610-0130-0010-0060.html

8. Montana Code Annotated 61-13-103, Seatbelt use required, exceptions. https://mca.legmt.gov/bills/mca/title_0610/chapter_0130/part_0010/section_0030/0610-0130-0010-0030.html

9. Montana Code Annotated 27-2-204, Tort actions. https://mca.legmt.gov/bills/mca/title_0270/chapter_0020/part_0020/section_0040/0270-0020-0020-0040.html

10. Montana Code Annotated 27-2-207, Actions for injury to property. https://mca.legmt.gov/bills/mca/title_0270/chapter_0020/part_0020/section_0070/0270-0020-0020-0070.html

11. Montana Code Annotated 61-6-103, Mandatory liability insurance. https://mca.legmt.gov/bills/mca/title_0610/chapter_0060/part_0010/section_0030/0610-0060-0010-0030.html

12. Montana Code Annotated 33-23-201, Uninsured and underinsured motorist coverage. https://mca.legmt.gov/bills/mca/title_0330/chapter_0230/part_0020/section_0010/0330-0230-0020-0010.html