Wyoming Chain Law for Trucks 2026: Level 1 & 2 Guide

Two Levels, Clear Consequences

Wyoming operates a two-level chain law system. Conditions are either hazardous (Level 1) or extremely hazardous (Level 2), and your options change accordingly. Unlike Colorado’s three separate chain and traction laws, Wyoming’s structure is straightforward — but the consequences of getting it wrong on I-80 are the same either way.

Level 1 vs. Level 2

Level 1 (Hazardous Conditions)

When WYDOT declares Level 1, you need one of: tire chains, adequate snow tires, or all-wheel drive. For commercial vehicles, chains must be on at least two drive wheels at opposite ends of the same drive axle.

Level 2 (Extremely Hazardous Conditions)

Level 2 narrows your options. Snow tires alone are no longer sufficient. You need either tire chains or AWD equipped with M+S (mud and snow) or all-weather-rated tires. The CMV placement requirement stays the same — two drive wheels, opposite ends of the same axle.

Important comparison: Wyoming’s CMV chain requirement is two wheels on one axle. California requires 8+ chains on a tractor-trailer; Oregon requires 4 on the primary axle. Wyoming’s standard is less restrictive than most neighboring states, but it is still mandatory when Level 2 is declared — AWD with all-season tires that are not M+S-rated is not sufficient.

What Counts as “Tire Chains” in Wyoming

Wyoming Statute WS 31-5-956(k) defines tire chains as: metal chains consisting of two circular metal loops (one on each side of the tire) connected by not less than nine evenly spaced chains across the tire tread, or any other traction device capable of providing traction equal to or exceeding that of metal chains under similar conditions.

This matters for two reasons:

1. Alternative devices are allowed. Textile traction devices such as AutoSock and similar products can be legal in Wyoming under the equal-traction standard. Cable chains also qualify if they meet the threshold. Wyoming does not use California’s Type G/Type W classification system — the standard is outcome-based.

2. “Adequate snow tires” is not the same as winter-rated tires. At Level 1, adequate snow tires are acceptable for CMVs only if they meet the traction threshold. At Level 2, this option is eliminated entirely for commercial vehicles.

If you are uncertain whether an alternative device qualifies, carry metal chains as the fallback.

Chain-Up Locations and Mile Markers

Three Sisters (I-80 MP 7–34)

The Three Sisters section of I-80 in southwest Wyoming — between Evanston and Bridger Valley — is the primary chain law activation zone on the interstate. This 27-mile stretch combines elevation, exposure, and the wind conditions that define I-80 to create the most challenging winter driving on Wyoming interstates.

Designated chain installation areas exist at MP 7 (westbound approach) and removal areas at MP 34. Do not stop in the travel lanes to install chains. Use these designated areas only.

What happens if you cannot chain up: If you reach a Wyoming Highway Patrol checkpoint during an active chain law and cannot comply, you are not just cited and waived through. You are turned around and directed back to the nearest community. There is no option to proceed through the Three Sisters or Teton Pass without meeting the chain requirement.

Walcott Junction and Summit

Two additional I-80 segments see regular activation: Walcott Junction near milepost 235 east of Rawlins, and the Summit/Telephone Canyon area near milepost 318 east of Laramie. Truckers who focus only on the Three Sisters miss these eastern segments.

South Pass (WYO 28)

South Pass between Farson and Lander is remote and high-elevation. Chain law activation here receives less highway patrol coverage than I-80, but conditions can be severe and the same requirements apply.

No Fixed Season — Condition-Based Activation

Wyoming has no statutory must-carry season. There is no date range equivalent to Colorado’s September 1–May 31 Must Carry Law. The chain law activates when WYDOT determines conditions warrant it, not by calendar.

From the Wyoming Highway Patrol: “State law does not specify any certain time of year when commercial vehicles must carry tire chains, but it’s a good idea for them to do so during the cold weather season.”

The practical window is October through April, with early-season storms in late September on South Pass and Teton Pass occasionally triggering it. Do not assume the season has not started because it is early October, or ended because it is late April.

How to Know When Chain Law Is Active

WYDOT provides multiple real-time notification channels:

wyoroad.info — Official WYDOT road conditions site. Search by route to see current chain law status, closures, blow-over risk, and reduced visibility warnings for specific segments.

511 by phone — Call 5-1-1 from any phone for current road conditions by route.

Wyoming 511 app — Downloadable app with real-time route alerts.

511 Notify (text and email subscription) — This is the most useful option for truckers running regular Wyoming routes. Sign up at wyoroad.info to receive push notifications for specific route segments when chain law activates, when closures occur, or when extreme wind or blow-over risk is declared. You can subscribe by route segment and receive separate day and night alerts. This is a free subscription service run by WYDOT.

Do not rely on memory of when the chain law was last active. Conditions can change in hours on Wyoming interstates.

Tread Depth Requirements (Same Statute)

Wyoming Statute WS 31-5-956(f) requires, regardless of chain law status:

• Front wheels of a bus, truck, or truck tractor: Minimum 4/32 inch tread depth
• All other wheels: Minimum 2/32 inch
• No tire may have exposed fabric through the tread or sidewall

Tread inspections can occur at the same checkpoints where chain compliance is verified. Vehicles that meet the chain law but fail tread depth requirements can still be placed out of service.

Penalties

The $750 penalty for causing a closure is a misdemeanor conviction, not just a civil fine. When a truck without adequate traction blocks I-80, the closure affects hundreds of vehicles. The fine is the smallest part of the cost.

The Wyoming Highway Patrol conducts compliance checks when the chain law is in effect — this is not passive enforcement. Troopers are stationed at chain-up areas and checkpoints when conditions warrant, particularly on the Three Sisters segment.

Chain Law and Insurance

Chain law violations enter your safety record and affect CSA scores. More significant is the insurance exposure from the accident that non-compliance causes.

If a driver without adequate traction causes an incident and investigators determine the chain law was active and the driver failed to comply, insurers may argue willful negligence to contest the claim. A carrier that instructs drivers to skip chain-up to save time is compounding that exposure significantly.

Proper Wyoming trucking insurance with adequate limits is the financial backstop — but chain law compliance is the first line of defense. The $250 fine is not the risk. The eight-figure liability exposure from a multi-vehicle incident on an icy I-80 is the risk.

Do not stop in the driving lane to install or remove chains. Use the designated chain-up areas at MP 7 and MP 34. Stopping in a travel lane on I-80 in reduced visibility creates the exact kind of incident that generates catastrophic claims.

Frequently Asked Questions

Do commercial vehicles need chains in Wyoming even with AWD?

At Level 1, AWD without chains is acceptable. At Level 2, AWD is only sufficient if the tires are M+S or all-weather-rated. If your AWD vehicle has standard all-season tires that are not M+S-rated, you need chains at Level 2.

How many chains does a semi-truck need in Wyoming?

At minimum, chains on two drive wheels at opposite ends of the same drive axle. This is less than California (8+ chains on a tractor-trailer) or Oregon (4 on the primary axle), but it is a mandatory minimum — not a suggestion.

Can I use cable chains or AutoSock instead of metal chains in Wyoming?

Wyoming law allows any traction device that provides traction equal to or exceeding metal chains. AutoSock and similar textile devices are marketed as meeting this standard in all 50 states. Cable chains generally qualify. If you use an alternative device, make sure it meets the standard and consider carrying metal chains as a backup.

What roads in Wyoming have chain laws most often?

I-80’s Three Sisters (MP 7–34) is the most frequently activated segment. Walcott Junction (MP 235) and Summit/Telephone Canyon (MP 318) also see regular activation. WYO 28 at South Pass and WY 22 at Teton Pass round out the high-frequency locations.

What happens if I can’t chain up at a Wyoming checkpoint?

You are turned around and directed to the nearest community. There is no option to proceed without meeting the chain requirement. Plan your chain-up before you reach the designated areas — once at the checkpoint, it is too late to backtrack and install.

When is Wyoming’s chain law in effect?

Wyoming has no statutory season. The chain law activates based on current road conditions, typically October through April, but it can be triggered in late September or late April as well. Subscribe to WYDOT’s 511 Notify service for real-time alerts on your specific routes.