South Dakota trailer laws and regulations
South Dakota trailer rules at a glance: registration thresholds, brake requirements, length, width, height limits, hitch, lighting, and safety chains.
South Dakota requires a license plate on any trailer under 6,000 lbs towed by a car, pickup, or van. The brake threshold is 3,000 lbs, max trailer width is 102 inches, max height is 14 ft, and a safety chain is required whenever you tow above 20 mph.
Quick reference
| Rule | South Dakota limit |
|---|---|
| Registration / plate | Required on trailers under 6,000 lbs towed by car, pickup, or van |
| Max combined length (tow + trailer) | 75 ft |
| Max trailer length | Not specified |
| Max twin-trailer length | 75 ft combined, second trailer ≤ 24 ft |
| Max trailer width | 102 in (excludes safety devices) |
| Max height (trailer + load) | 14 ft |
| Trailer brakes required | Over 3,000 lbs (trailers); over 7,000 lbs (semi trailers), subject to wheel-weight rule |
| Safety chain or cable | Required above 20 mph |
| Mirrors | Must see 200 ft behind |
Source: South Dakota Codified Laws Title 32 (Motor Vehicles), administered by the Department of Public Safety.
Registration
Trailers under 6,000 lbs towed by a car, pickup, or van need a license plate renewed annually. Once licensed, there is no further weight limit beyond your tow vehicle’s gross weight rating.
Trailers towed by commercial trucks can use an identification plate instead of a regular license if they are registered under the declared gross weight system.
Dimensions
- Max combined length (truck plus trailer): 75 ft including bumpers, excluding safety and energy conservation devices.
- Max twin-trailer length: 75 ft combined, with the second trailer no longer than 24 ft.
- Max trailer width: 102 in (clearance lights, mirrors, and safety devices do not count toward width).
- Max trailer height including load: 14 ft.
The state does not publish a max single-trailer length, but the 75 ft combined cap still applies.
Hitch and safety chains
If you are towing above 20 mph on a public highway, you must use a safety chain, cable, or equivalent device in addition to the primary hitch or coupler.
A standard ball hitch on the bumper or frame is allowed but still needs a safety chain. The only exemption is a semi trailer using a 5th wheel and kingpin assembly that meets Interstate Commerce Commission standards.
Lighting
The minimum lighting required matches federal FMVSS standards: tail lights, brake lights, turn signals, license plate light, and reflectors.
Trailers and semi trailers manufactured before July 1, 1973 can run with a single red tail lamp on the left side, visible from 500 ft. Anything built after that date needs the full lighting package.
If you tow with a 2021 to 2026 Ford F-150, 2022 to 2026 Super Duty, Ranger, Expedition, Maverick, Transit, or Lincoln Navigator, check the status of recall 26C10 (NHTSA 26V104000). It covers Integrated Trailer Module software faults that affect trailer lights and brakes. Ford pushed an OTA fix in March 2026.
Speed limits
No special speed limit applies to towing a trailer in South Dakota. You still cannot exceed the posted limit, and an officer can stop you if the trailer is swaying or otherwise hazardous even when you are under the limit.
Mirrors
Mirror specifications are not spelled out in statute, but drivers must be able to see at least 200 ft of road behind their vehicle. If the trailer blocks the interior mirror, side mirrors or mirror extenders that achieve that view are required.
Brakes
The South Dakota brake rules:
- Trailers and semi trailers must have a braking system operable from a single device in the tow vehicle.
- Trailers under 3,000 lbs (and semi trailers under 7,000 lbs) are exempt from the all-wheels-braked rule if both conditions are met:
- The trailer’s wheel weight does not exceed 40% of the tow vehicle’s gross weight when connected.
- The combination still meets all other braking performance requirements.
In practice, a single-axle utility trailer over 3,000 lbs needs working brakes. A Tekonsha, Curt, or Redarc brake controller wired into your tow vehicle satisfies the “controlled from a single device” requirement.