South Dakota's motorcycle rules surprise a lot of riders because they cut in two different directions. The helmet law is narrow: once you turn 18, the state stops telling you what to wear on your head. Lane use is the opposite: there is no age cutoff and no exception for a slow-moving jam on I-90. Both facts, and where the state draws the line on each, come from a specific set of Codified Laws worth knowing before you're stopped by a trooper, or worse, sitting across from an insurance adjuster after a crash.
Who actually has to wear a helmet
South Dakota only requires a helmet for riders and passengers under 18. SDCL 32-20-4 makes it illegal for anyone under that age to operate or ride a motorcycle unless they're wearing a protective helmet meeting federal Motor Vehicle Safety Standard 218, and it separately bars an operator of any age from carrying an under-18 passenger who isn't wearing one.1 The statute freezes the safety standard as it existed on January 1, 1984, so the compliance question in a South Dakota courtroom is still whether the helmet met that decades-old federal spec, not a current one.
An adult riding solo, or with an adult passenger, owes no helmet duty at all under South Dakota law. Violating the minor's helmet rule is a Class 2 misdemeanor, which carries up to 30 days in county jail, a $500 fine, or both.2 Riders inside an enclosed cab, think of a three-wheeled autocycle with a roof, are exempted from the helmet requirement entirely under SDCL 32-20-4.2.3
Eye protection applies no matter your age
Where the helmet law stops at 18, South Dakota's eye protection rule doesn't. SDCL 32-20-4.1 requires every motorcycle operator, of any age, to wear an eye protective device or ride a motorcycle equipped with a windscreen tall enough to shield the operator's eyes in a normal riding position.4 It's a lesser charge, a petty offense rather than a misdemeanor, but it applies universally in a way the helmet law doesn't. The same section bans riding with eyewear tinted below 35 percent light transmittance during the hours headlights are required, so mirrored or heavily tinted sunglasses become a violation after dusk. The enclosed-cab exemption in SDCL 32-20-4.2 covers this requirement too.
What "lane splitting" actually means here
South Dakota bans lane splitting outright, for every rider, with no speed threshold and no traffic-jam exception. The core prohibition sits in SDCL 32-20-9.3: no one may operate a motorcycle between adjacent lanes of traffic, or between adjacent lines or rows of vehicles.5 It's a Class 2 misdemeanor, the same penalty tier as the helmet violation.
Two companion statutes reinforce it. SDCL 32-20-9.1 entitles a motorcycle to full use of its lane and bars any other vehicle from squeezing a rider out of it,6 and SDCL 32-20-9.2 separately forbids a motorcyclist from overtaking and passing another vehicle within the same lane that vehicle already occupies.7 Together, the three sections close off every version of splitting: riding the stripe between two lanes of moving cars, threading stopped traffic at a red light, or passing a car from inside its own lane.
There's one carve-out, and it's easy to confuse with lane splitting because it also involves sharing a lane. SDCL 32-20-9.5 lets up to two motorcycles ride side by side within a single lane,8 and the 9.2 overtaking ban has a matching exception for motorcycles, or a motorcycle and a bicycle, riding two abreast. That's a rule about formation riding, not about filtering between vehicles, and it caps out at two bikes. Officers on duty are exempted from the lane-use restrictions under SDCL 32-20-9.4.
The crash numbers behind the law
South Dakota's own 2024 crash data shows why regulators treat lane discipline and helmets as separate problems. Motorcycles were involved in 502 reported crashes that year, just 2.7 percent of all crashes statewide, but they accounted for 24.6 percent of fatal crashes and 33 rider deaths, up from 29 the year before.9 Helmet use among crash-involved motorcycle drivers sat at 48.8 percent, essentially a coin flip.9
Broken out by age, compliance was highest exactly where the law requires it: 85.7 percent of 16-to-17-year-old riders in crashes wore a helmet, versus just 39.7 percent of riders 45 and older, the group the law doesn't touch at all.9 Among the 33 people killed on motorcycles in 2024, only ten wore any kind of helmet; thirteen wore no protective safety equipment whatsoever.9 Young riders showed up disproportionately in the riskiest crashes, too: drivers under 20 held just 0.7 percent of the state's motorcycle licenses but made up 16.9 percent of the speeding drivers involved in motorcycle crashes that year.9
Getting licensed to ride legally
Riding legally in South Dakota means holding a Class M endorsement, available starting at 16 after a vision test, an 80-percent written knowledge test, and a road skills test.10 A motorcycle safety course is mandatory for applicants under 18, funded through a dedicated state fee under SDCL 32-20-14.11 Riders 18 and older can skip the course, though completing an approved Basic Rider Course within a year of licensing waives the written and skills tests. The South Dakota Safety Council runs those courses under contract with the Department of Public Safety, April through October, and administers the license test as the final step.10
If you're hurt in a crash
South Dakota is an at-fault state: the driver who caused the crash, or their insurer, pays, with minimum liability coverage set at $25,000 per person and $50,000 per accident for bodily injury.12 Because that floor is thin next to the cost of a serious motorcycle injury, the uninsured and underinsured motorist coverage built into every policy at the same limits matters more here than it does in a typical car-on-car claim.13
Not wearing a helmet doesn't create liability by itself, and South Dakota law has never treated it as negligence in causing a crash. But an insurer defending a claim can still argue it affected how badly you were hurt. That argument lands inside South Dakota's unusual fault rule: under SDCL 20-9-2, a jury has to find your own negligence "slight" compared to the other driver's before you can recover anything at all, and it's a qualitative call for the jury rather than a fixed percentage.14 A helmet-and-eyewear argument aimed at injury severity can push that comparison the wrong way, which is one more reason to get medical documentation of what you were wearing and using at the time of the crash. There's no cap on what a jury can award for pain and suffering either way; South Dakota's old statutory cap on general damages was struck down as unconstitutional almost thirty years ago.15
You have three years from the crash date to file a personal injury claim, or until age 18 plus three years if you were a minor when it happened.16 A separate six-year window applies to property damage claims on the bike itself, twice as long as the injury clock. If the crash left you sorting out a diminished value claim on top of repairs, that's covered on our South Dakota diminished value page.17 You can also pull the official report through our South Dakota crash report page. And if you're deciding whether to bring in a lawyer, our legal directory lists attorneys who handle South Dakota motorcycle cases.
This is general information, not legal advice.
Sources
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SDCL 32-20-4, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-4
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SDCL 22-6-2, South Dakota Legislature - https://sdlegislature.gov/Statutes/22-6-2
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SDCL 32-20-4.2, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-4.2
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SDCL 32-20-4.1, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-4.1
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SDCL 32-20-9.3, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-9.3
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SDCL 32-20-9.1, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-9.1
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SDCL 32-20-9.2, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-9.2
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SDCL 32-20-9.5, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-9.5
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SD Department of Public Safety, 2024 South Dakota Motor Vehicle Traffic Crash Summary Facts Book - https://www.safesd.gov/downloads/crash-summary/2024-South-Dakota-Motor-Vehicle-Traffic-Crash-Summary-Facts-Book.pdf
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SD Department of Public Safety, Motorcycle License - https://dps.sd.gov/driver-licensing/motorcycle-license
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SDCL 32-20-14, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-20-14
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SDCL 32-35-70, South Dakota Legislature - https://sdlegislature.gov/Statutes/32-35-70
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SDCL 58-11-9 and SDCL 58-11-9.4, South Dakota Legislature - https://sdlegislature.gov/Statutes/58-11-9
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SDCL 20-9-2, South Dakota Legislature - https://sdlegislature.gov/Statutes/20-9-2
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Knowles v. United States, 1996 SD 10, 544 N.W.2d 183, CourtListener - https://www.courtlistener.com/opinion/7930885/knowles-v-united-states/
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SDCL 15-2-14(3) and SDCL 15-2-22, South Dakota Legislature - https://sdlegislature.gov/Statutes/15-2-14
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SDCL 15-2-13(4), South Dakota Legislature - https://sdlegislature.gov/Statutes/15-2-13