Truck Chain Requirements

Frequently Asked Questions

What are the dates for the chain law?

California does not have any specific dates when vehicles are required to carry chains. When the road is posted with a sign requiring chains, all heavy-duty vehicles (over 6,500 pounds gross weight) must be equipped with chains mounted on the tires in order to proceed. Depending on the severity of road conditions, some vehicles (passenger cars, 4-wheel drive vehicles with snow tires) may not be required to install chains at that point. The exceptions will be posted on the sign.

What are tire traction devices?

Tire traction devices are defined in the California Vehicle Code (VC) Section 605 as “devices or mechanisms having a composition and design capable of improving vehicle traction, braking, and cornering ability upon snow or ice-covered surfaces,” and include conventional link-type tire chains and cable chains, as well as other less conventional devices such as “Spikes Spyder.” When the term “chains” is used here, it means any “tire traction device” unless it specifically states link-type chain.

What are Automatic Traction Devices (A.T.D.'s) and are they legal in California?

Automatic Traction Devices (A.T.D.'s) are used primarily on commercial vehicles, emergency vehicles, and busses. ATD's are devices mounted under the vehicle that sling chain segments under the inside drive wheels. These devices can be deployed by the driver when the need for extra traction is required. While they are legal in California and have been approved as a direct one-on-one replacement for conventional chains, vehicles with only ATD's may be required to add additional chains to outside wheels to comply with the California Chain Requirements Chart.

What chains are required for an “18-wheeler?”

An 18-wheeler (typically a combination consisting of a 3-axle tractor and 2-axle semitrailer, but including other combinations and axle counts) is required to have chains on:

  • All four outside tires on the main (usually front) drive axle
  • The two outside tires on the other (usually rear) drive axle
  • One tire on each side of the trailer (front or rear axle, or staggered OK)
  • No chains are required on the steering axle

Diagrams illustrating chain placement: Chain Requirements (PDF) .

Are combinations consisting of a 2-axle tractor (single drive axle) and double trailers prohibited from chain control areas?

There are some areas where such combinations are prohibited when chain controls are posted. These routes are marked with posted signs indicating the restriction.

Are chains required on the inside “duals” on 2-axle vehicles (trucks, buses, RVs, etc.)?

Not usually, but under severe conditions, the California Department of Transportation (Caltrans) may require chains on the inside duals if conditions warrant. (If conditions are this severe, it may be better to postpone the trip.)

Where are chains required?

Chains are most often required in the higher mountain passes of northern California, such as Interstate 5 north of Redding, Interstate 80 over Donner Pass between Sacramento and Reno, Nevada, and US Highway 50 over Echo summit between Lake Tahoe and Sacramento. Chains are also sometimes required on State Route 58 near Tehachapi between Bakersfield and Mojave, Interstate 15 over Cajon Pass between Victorville and San Bernardino, and Interstate 5 over Tejon Pass between Los Angeles and Bakersfield. However, snow can fall unseasonably at higher elevations at many locations within California. Chains may be required at any time at these higher elevations when conditions warrant.

Motorists are advised to check the Caltrans website for current road conditions. Motorists may also call the Caltrans road information number at 800-427-7623.

Are “all-weather” or “all-terrain” tires the same as “snow” tires?

They may be. Snow tires have the designation “Mud & Snow” or an abbreviation such as “M-S,” “M+S,” or “M/S” marked on the tire sidewall. Tires without this designation are not considered snow tires. Snow tires must also have at least 6/32-inch (3/16”) of tread depth (about 1/2 of the original tread depth).

Are cable chains permitted?

Usually. They are permitted for passenger cars and light trucks under virtually all conditions. Cables are not as effective as link-type chain under severe conditions at higher elevations and steep grades for “big-rigs” and may not be permitted depending on local conditions as determined by Caltrans. Whenever chain controls are posted over Donner Pass on Interstate 80, heavy trucks are usually required to have link-type chain on at least the main drive axle.

Must chains be carried in exempted vehicles?

Vehicles without chains are not permitted to enter chain control areas and must return to a lower elevation where chains are not required. There is no provision to park vehicles at chain control check points.

What does it mean when the radio road information says “trucks are being screened?”

During inclement or unsettled weather conditions, Caltrans may set up truck screening check points at approaches to major mountain highways. When these screens are present, all heavy-duty trucks must stop and show Caltrans personnel that they have the required chains on board to proceed. Trucks without chains will be directed to return to a lower elevation until weather improves. There is no room available at higher elevations to park trucks not equipped with chains.

What are the dates for studded snow tires?

Studded snow tires are permitted in California from November 1 until April 30 each year. During this time, studded tires are permitted in any location within the state. Studded snow tires are not considered tire traction devices and may not be used in lieu of chains.

If I have 4-wheel-drive, do I need to carry chains?

Yes. Even though weather conditions may not warrant the use of chains on 4-wheel-drive vehicles at a particular time, to enter a chain control area, you must have a set of chains (for one drive axle) for your vehicle in your possession. If conditions worsen or you have trouble controlling your vehicle, you must stop and install the chains.

If I have snow tires, do I need to carry chains?

Yes. Even though weather conditions may not warrant the use of chains on passenger vehicles equipped with snow tires at a particular time, to enter a chain control area, you must have a set of chains (one pair) for your vehicle in your possession. If conditions worsen or you have trouble controlling your vehicle, you must stop and install the chains.

If I have snow tires on a heavy-duty commercial vehicle, do I need to carry chains?

Yes. There is no exemption for heavy-duty commercial vehicles (over 6,500 pounds gross weight) equipped with snow tires. Chains must be installed on heavy-duty commercial vehicles whenever chain controls are posted.

If I have studded snow tires, do I need to carry chains?

Yes. Studded snow tires are not considered tire traction devices and may not be used in lieu of chains.

Is “all-wheel drive” the same as 4-wheel drive?

Yes. Even though all-wheel drive systems may differ mechanically from conventional 4- wheel drive systems, for the purposes of chain control, all-wheel drive is considered the same as 4-wheel drive.

The manufacturer of my vehicle recommends that chains not be installed on it. Do I still have to put on chains?

Yes. Many vehicles which will not accommodate conventional link-type chains will accommodate cable chains or other devices such as “Spikes Spider.” If your vehicle is not equipped with some type of tire traction device, it is neither safe nor lawful for you to enter a chain control area. If you choose not to install tire traction devices on your vehicle, you may not enter a chain control area.

Which axle do I install the chains on?

Chains must be installed on the drive axle. All-wheel drive vehicles and 4-wheel drive vehicles may have chains installed on either drive axle, but the rear axle is preferred, unless the vehicle manufacturer recommends the front axle.

Do I have to put on chains when I am towing a trailer?

Yes, always.

Even if I have 4-wheel drive?


Do I have to put chains on the trailer?

You must have at least one axle chained if the trailer is equipped with brakes.

What are the R-1, R-2 conditions that I hear about?

Although Caltrans does not post signs with these designations nor use them to announce chain controls to the public, they are used internally within Caltrans and the CHP as a kind of shorthand to describe chain restrictions and may be included in traffic reports disseminated by various news outlets.

There are three primary categories of chain restrictions, as shown below:

Requirement 1 (R-1): Chains are required on all vehicles except passenger vehicles and light-duty trucks under 6,000 pounds gross weight and equipped with snow tires on at least two drive wheels. Chains must be carried by vehicles using snow tires. All vehicles towing trailers must have chains on one drive axle. Trailers with brakes must have chains on at least one axle.

Requirement 2 (R-2): Chains are required on all vehicles except four-wheel-drive vehicles under 6,500 pounds gross weight and equipped with snow tires on all four wheels. Chains for one set of drive wheels must be carried by four wheel-drive vehicles using snow tires.

Requirement 3 (R-3): Chains are required on all vehicles without exception.

R-1 and R-2 are the most common conditions. A highway will often be closed before an R-3 condition is imposed. Some local areas may use variations of these designations. You must follow the directions on the signs posted for chain controls or any instructions given by Caltrans or CHP personnel at chain control check points, even if these are at variance with broadcast road condition reports or information contained herein.

What California Vehicle Code sections refer to chains?

Chain requirements are covered in the CVC, Section 605 and Sections 27450 to 27503. In addition, Section 26104 also covers laboratory testing (see below).

26104. (a) Every manufacturer who sells, offers for sale, or manufactures for use upon a vehicle devices subject to requirements established by the department shall, before the device is offered for sale, have laboratory test data showing compliance with such requirements. Tests may be conducted by the manufacturer.
(b) The department may at any time request from the manufacturer a copy of the test data showing proof of compliance of any device with the requirements established by the department and additional evidence that due care was exercised in maintaining compliance during production. If the manufacturer fails to provide such proof of compliance within 30 days of notice from the department, the department may prohibit the sale of the device in this state until acceptable proof of compliance is received by the department.