South Dakota Lane Splitting: Banned Outright, but Two Riders May Share One Lane

South Dakota packs its whole answer into five consecutive sections enacted together as SL 1970, ch 176, and they have to be read as a set because each one qualifies the next.

SDCL 32-20-9.1 grants the entitlement. All motorcycles are entitled to full use of a lane, and no motor vehicle may be driven in such a manner as to deprive a motorcycle of the full use of a lane. That is a duty on car drivers, enforceable as a Class 2 misdemeanor against the driver who crowds a rider. But the section carries its own trade-off: it does not apply to motorcycles operated two abreast in a single lane. A rider who pairs up gives away the statutory claim to the whole lane.

SDCL 32-20-9.2 bans same-lane overtaking. The operator of a motorcycle may not overtake and pass in the same lane occupied by the vehicle being overtaken. It carries two carve-outs that are unusual in their specificity: motorcycles operated two abreast in the same lane, and a motorcycle and a bicycle operated two abreast in the same lane. So a rider may legally sit alongside a bicycle in one lane in South Dakota, which is a scenario most state codes leave unaddressed.

SDCL 32-20-9.3 is the lane splitting ban itself, and it is written broadly. No person may operate a motorcycle between adjacent lanes of traffic, or between adjacent lines or rows of vehicles. The second clause matters as much as the first: it reaches queues on an undivided road and traffic backed up at a light, not just marked lanes. Nothing in the section conditions the ban on traffic speed, on the presence of stopped vehicles, or on road type, so South Dakota has neither a California-style authorization nor a Utah- or Arizona-style filtering allowance.

SDCL 32-20-9.4 supplies the only exemption. Sections 32-20-9.2 and 32-20-9.3 do not apply to police officers in the performance of their official duties. Note what it does not cover: the two-abreast cap in 32-20-9.5 and the full-lane entitlement in 32-20-9.1 are outside its reach.

SDCL 32-20-9.5 caps lane sharing at two. No person may operate a motorcycle more than two abreast in a single lane, so a third rider cannot join the pair.

Who these rules bind is broader than the word motorcycle suggests. SDCL 32-20-1(3) defines motorcycle for this chapter to include motorbikes, mopeds, bicycles with a motor attached, and all motor operated vehicles of the bicycle or tricycle type with a saddle or a standing platform, while expressly excluding an electric bicycle as defined in SDCL 32-20B-9 and a multi-passenger quadricycle. A moped rider filtering to the front of a queue is therefore committing the same offense as a rider on a full-size machine.

Underneath all of this sits the general lane discipline rule at SDCL 32-26-6, which requires any vehicle on a roadway divided into lanes to be driven as nearly as practicable entirely within a single lane and forbids leaving that lane until the driver has ascertained the movement can be made safely. SDCL 32-26-5 switches those rules on wherever a roadway carries two or more clearly marked lanes.

Every one of the motorcycle lane sections is a Class 2 misdemeanor, which SDCL 22-6-2(2) caps at thirty days in a county jail, a five hundred dollar fine, or both, plus restitution to any victim under chapter 23A-28. 4, which creates no offense at all. Enforcement is by the Division of Highway Patrol and by county and municipal officers; SDCL 32-21-28 lets a patrol officer stop a vehicle and inspect it on evidence of nonconformance with chapters 32-14 to 32-19 or 32-22 to 32-34, and SDCL 32-21-29 lets any peace officer issue a warning ticket requiring correction within ten days instead of charging.

1's full-lane entitlement is what a rider would otherwise rely on to argue a driver caused a collision. Local governments cannot legalize the practice within their limits: SDCL 32-14-3 bars local authorities from enacting or enforcing any rule or regulation contrary to chapters 32-14 to 32-19 and 32-22 to 32-34.