And here's the information from the Oregon D.O.T.
--'rocco
Chain Law
Oregon's chain law applies to all highways throughout the state. When you drive in winter conditions, you may see signs telling you to carry chains or traction tires and when you are required to use them. In some areas, lighted message signs also will advise you about chaining up. Traction tires may be used in place of chains on vehicles rated at 10,000 pounds gross vehicle weight or less and that are not towing or being towed.
In very bad winter road conditions all vehicles may be required to use chains regardless of the type of vehicle or type of tire being used. This is known as a conditional road closure. A conditional road closure may occur on any of Oregon's highways and are frequent in the winter on Interstate 5 through Siskiyou Pass south of Ashland.
Studded tires are legal in Oregon from November 1 to April 1. Because of the damage caused by studded tires, the Department of Transportation encourages motorists to use studded tires only when necessary. Delaying putting on studded tires or using other traction tires is helpful to the condition of the highways.
For placement of chains or traction tires go to Minimum Chain Requirements. For information on traction tires go to Traction Tires.
Signs
Signs like these will be posted to let you know the current requirements for chains and traction tires:
You must have chains or traction tires in or on your vehicle and they must be the right size for your vehicle and of sufficient number to comply with the chain laws.
You must use chains if your vehicle is towing or rated more than 10,000 pounds gross vehicle weight (GVW). Chains must also be used on a trailer or vehicle being towed if it has a brake that operates while in tow.
You must use chains if your vehicle is towing or is rated over 10,000 pounds GVW. Chains must also be used on a trailer or vehicle being towed if it has a brake that operates while in tow. If your vehicle is rated 10,000 pounds GVW or less and is not towing you must use chains or traction tires.
Definitions
"Chains" include link chains, cable chains, or any other device that attaches to the wheel, vehicle or outside of the tire that is specifically designed to increase traction on ice and snow conditions. For information on the placement of chains go to Minimum Chain Requirements.
"Traction Tires" are studded tires or other tires that meet the tire industry definition as suitable for use in severe snow conditions. These tires are marked with a mountain/snowflake emblem on the sidewall like this:
For information on tires that meet the tire industry definition as suitable for use in severe snow conditions, contact your tire dealer or the Northwest Tires Dealers Association. When allowed in place of chains, traction tires are to be placed as shown on Minimum Chain Requirements.
Studded tires are legal for use in Oregon from November 1 to April 1. The studs must be made of a rigid material that wears at the same rate as the tire tread. Studs must extend at least .04 inch but not more than .06 inch beyond the tread surface.
Exemptions
In typical winter conditions, the following vehicles are completely or partially exempt from the chain law. However, in very bad winter road conditions all vehicles may be required to use chains regardless of the type of vehicle or type of tire being used (this is known as a conditional road closure). A conditional road closure may occur on any of Oregon's highways and are frequent in the winter on Interstate 5 through the Siskiyou Pass south of Ashland:
1. Police vehicles, and fire vehicles, ambulances, and Department of Transportation highway maintenance vehicles when performing their duties.
2. A four-wheel or all-wheel drive passenger vehicle if all of the following statements are true:
a) It has an unloaded weight of 6,500 pounds or less;
b) It is operated to provide power to both the front and rear wheels;
c) It is carrying chains;
d) It has mud and snow, all-weather radial, or traction tires on all of its wheels;
e) It is not towing another vehicle;
f) It is not being operated in a manner or under conditions that cause the vehicle to lose traction.
3. Utility company vehicles, such as water, power, or heat, when providing emergency response services.
4. A bus that is over 10,000 pounds gross vehicle weight (GVW) due only to accessibility modifications for disabled persons is exempt from the chain requirements for vehicles rated over 10,000 GVW unless it is towing or being towed.
5. Motorcycles are exempt from the requirement to carry chains or traction tires and may not travel when chains or traction tires are required on all or certain vehicles.
Note: Although exempt, ODOT vehicles use mud and snow tires and chains in most winter situations. Studded tires are not used on ODOT vehicles because of the damage such tires cause to the highway.
Penalties
Drivers who disobey the signs requiring chains or traction tires are subject to a class C traffic infraction.