Wyoming trailer laws and towing rules
Wyoming's 85-foot combo length, brake threshold, lighting requirements, and mirror rules for legal towing, with relevant Title 31 statute references.
Wyoming allows combination lengths up to 85 ft (one of the most permissive in the country) and requires brakes on trailers over 3,000 lb gross weight. Max trailer length is 45 ft, max width 102 inches, max height 14 ft. Tandem trailers are permitted within the 85 ft total.
Wyoming statutes covering this material live in Title 31, primarily 31-5-952 through 31-5-961 (lighting and equipment) and 31-18-801 through 31-18-802 (dimensions).
| Requirement | Wyoming rule |
|---|---|
| Trailer brake threshold | 3,000 lb gross weight |
| Max combo length | 85 ft |
| Max single trailer length | 45 ft |
| Tandem trailers | Permitted within 85 ft total |
| Max width | 102 inches (excluding state-approved safety devices) |
| Max height | 14 ft |
| Mirrors | Two required: one driver-side, one interior or passenger |
| Speed limit while towing | Posted limit |
| Service brake performance | Stop the combination in 40 ft from 20 mph on dry level surface |
Length: Wyoming runs longer than most states
The 85 ft combination limit is well above the 65 ft typical in most states. This makes Wyoming a corridor for haulers running long combinations, but it also means a single trailer can stretch up to 45 ft (compared to typical 40 ft elsewhere).
Tandem trailers are allowed within that 85 ft limit. Both trailers in a tandem must independently meet lighting, braking, and safety chain requirements.
Brake requirements
Trailers and semitrailers with a gross weight over 3,000 lb must have brakes on all wheels. The 3,000-lb threshold is the most common state requirement and matches federal recommendations.
Combination performance standard: a service brake system that will stop the combination of vehicles within 40 ft from an initial speed of 20 mph on a level, dry, smooth, hard surface.
Parking brake: must hold all units on any grade under any load and weather condition.
Exception: a trailer under 40% of the gross weight of the towing vehicle may be towed without trailer brakes if the tow vehicle can stop the combination within the 40-ft rule above.
Breakaway protection is required on trailers equipped with brakes, applying brakes automatically if the trailer separates.
Lighting
Required lighting on the last trailer in any tow:
- Two tail lamps (red) on the rear.
- Two or more red reflectors on the rear.
- Two or more stop lamps.
- Electric flashing turn signals (left and right).
- Side marker lamps and reflectors per FMCSR standards for commercial use.
If the trailer is over 80 inches wide, clearance lamps (amber on front, red on rear) and identification lamps are required.
All lighting on the rearmost trailer must be functional and visible from the lead vehicle.
Dimensions
Trailer length max 45 ft. Combination max 85 ft including the tow vehicle and any trailers. Width max 102 inches (mirrors and state-approved safety devices excluded). Height max 14 ft.
Loads that exceed these dimensions need an oversize/overweight permit from the Wyoming Department of Transportation. Daily, weekly, and annual permits are available; pricing varies by load dimensions and weight.
Mirrors
Wyoming requires at least two rearview mirrors:
- One on the driver’s side (exterior).
- One either inside on the windshield (right of the driver) or on the passenger-side exterior.
If the trailer or load blocks the view from stock mirrors, extended tow mirrors are functionally necessary and effectively required to meet the rearward-view standard.
Hitch and safety chains
Wyoming statutes don’t specify a maximum drawbar length the way some states do, but general roadworthiness rules apply. The trailer must track true behind the tow vehicle; visible swerving or fishtailing can result in being pulled over.
Safety chains or cables are required as a secondary connection for all bumper-pull trailers. Fifth-wheel and gooseneck setups don’t require chains as the primary coupling is mechanical.
Speed limits
No specific reduced speed limit for towing. The posted limit applies, with rural interstate speeds in Wyoming reaching 80 mph in stretches. Towing at 80 mph is legal where posted, but most trailer tires are rated for a maximum of 65 or 75 mph (ST-rated tires) regardless of speed limit. Running ST tires above their rating is the most common cause of trailer tire failures on long Wyoming hauls.
LT-rated truck tires installed on a trailer hub can rate higher, but they’re a less common setup. Check the tire sidewall, not the speed limit, before running fast.
Registration
Trailers in Wyoming require registration and plates. Counties handle registration through their treasurer’s office. Wyoming charges based on factory weight and a vehicle valuation that depreciates with age.
Things specific to Wyoming travel
Mountain passes and grades are everywhere. Combinations near the 85 ft limit need to manage downhill brake heat. Engine braking, transmission downshifting, and proper trailer brake controllers (Tekonsha Prodigy or similar, properly calibrated) reduce risk.
High wind on I-25, I-80, and US-30 corridors regularly closes roads to “light, high-profile vehicles,” which includes most enclosed and box trailers. WYDOT 511 shows current restrictions and is worth checking before a long haul.
Winter conditions: tire chains are sometimes required on grades. Wyoming chain law triggers on specific routes when conditions warrant.
What to keep handy
WYDOT Permits Office for oversize loads.
Wyoming Statutes Title 31 if you want the source text. Justia and FindLaw both host current versions.
WYDOT’s 511 system for road and weather conditions, accessible by phone or app.