Studded tires are only legal Nov. 1 - Mar. 31. Motorists using studded tires after the deadline could incur a $124 fine from the Washington State Patrol.
WSDOT, along with the local tire industry, wants motorists to know there is a variety of snow and studded tire alternatives available so they can choose the best tire for the conditions they’ll face. Since different types of winter tires provide varied performance under different road conditions, tire dealers can assist motorists to select the best option for them. Visit your local tire dealer to find out more.
Approved traction tires have at least an eighth of an inch of tread and are labeled “Mud and Snow,” “M+S,” “MS,” “All Season,” or have a “Mountain/Snowflake,” symbol. These tires can be used year-round. Studded tires are approved traction tires but are only legal between November 1 and March 31.
Tire chains come in many varieties such as “cross link,” “cable chains,” and plastic or nylon chains. All are legal for passenger vehicles when “CHAINS REQUIRED” signs are posted. Minimum chain requirements for commercial vehicles can be found at Washington State Patrol's Commercial Vehicle Division Web site.
What’s the matter with the studded tire?
First is the issue of safety. On untreated icy roads at or near freezing (32ºF) studded tires do provide some measure of improved stopping ability, but on a statewide average these (glare ice) road conditions occur less than 1 percent of the time in Washington. It is anticipated that the frequency of these events will continue to decrease as WSDOT continues to implement proactive snow and ice control practices.
WSDOT is particularly concerned about the use of studded tires in areas where motorists are exposed more to wet conditions than icy or glazed road conditions. WSDOT wants to make sure motorists are aware of the safety issues regarding studded tire performance in wet conditions.
Under wet driving conditions the stopping ability of vehicles equipped with studded tires is actually reduced. Tire studs reduce the full contact between a tire’s rubber compound and the pavement. Research on studded tires consistently shows that vehicles equipped with studded tires require a longer stopping distance on wet or dry pavement than do vehicles equipped with standard tires.
Also an issue for WSDOT is the accelerated pavement damage done to roadways by studded tires. The abrasion on pavement surfaces caused by studded tires wears down pavement at a much greater rate than do other types of tires.
Detailed report released March 2006 on The Study of Pavement and Studded Tire Damage. (pdf 1.9 mb)
What are the national developments on studded tires?
Much of the research on studded tires comes from Finland and Sweden where studded tire use is heavy in the winter months. U.S. studies concentrate on states like Alaska, where lightweight studs have been advocated, and Minnesota and Michigan where all studs have been banned since the early 1970’s. These studies all agree on one finding: pavement wear and rutting due to studded tire use is substantial and costly.
Nationwide, 36 states (including the District of Columbia) allow studded tires but restrict their use seasonally, geographically, or through equipment specifications. Six states (Colorado, Kentucky, New Hampshire, New Mexico, Vermont, and Wyoming) allow virtually unrestricted use of studded tires on state roads and highways.
Seven states (Alabama, Florida, Hawaii, Illinois, Louisiana, Mississippi, and Texas) currently prohibit the use of studded tires under any circumstances; however, out of these states only Illinois has significant amount of ice and snow.
Ultimately, WSDOT would like to see the use of tire studs phased out to improve safety and reduce pavement maintenance and preservation costs. Meanwhile, WSDOT hopes the trend will at least move to the introduction of new, even lighter weighted studs. If motorist use studs weighing no more than 1.1 grams – the stud of choice in Scandinavian countries – the potential of pavement wear in Washington would be reduced by an additional 36 percent.
Unfortunately, most states have yet to adopt the use of lighter weighted studs leaving out incentives for companies to ‘re-tool’ manufacturing & installation equipment to accommodate the new demand. Currently, the typical tire stud for approximately 85 to 90 percent of passenger cars in the United State weighs about 1.7 to 1.9 grams.
What’s next?
Winter has arrived and WSDOT officials do advise drivers to carry tire chains, monitor weather forecasts and the WSDOT website if driving mountain pass highways.
WSDOT will continue to provide information on developments surrounding the tire issue. The Washington State Patrol will continue to monitor and enforce the legal time allowed for studded tires use.
WSDOT crews will also continue their efforts to provide the best snow and ice control services like snow plowing and sanding, especially for those areas encumbered by severe winter conditions.
Remember the key elements to driving safely in winter – ice and snow, take it slow.
Please share with us your ideas, comments, and concerns on studded tires by contacting: WSDOTWinterOperations@wsdot.wa.gov