Studded tires are legal in Washington State and are typically allowed to be used each winter between the months of November and April. They are known to cause accelerated wheelpath wear resulting in additional pavement preservation costs. While studded tire use rates are hard to quantify, the volume of studded tire equipped vehicles is rather consistent across Washington State. This report uses Washington State Pavement Management System (WSPMS) data to explore studded tire wear on Washington State Department of Transportation (WSDOT) roads.
The average Portland Cement Concrete (PCC) pavement wears at about 0.01 inches per 1 million studded tire vehicle passes. The highest wear rates are near 0.5 mm/yr on I-90 in the Spokane area, while the lowest wear rates are in the range of 0.04-0.09 mm/yr in many locations. Stud wear rates are generally higher in the first 5 years of PCC pavement life and much less thereafter. Although excessive stud wear problems are limited and not a widespread issue, specific locations with high stud wear rates are alarming. While several strategies have been attempted to limit stud wear, none outside of diamond grinding has proven effective.
There are a few new materials (resin modified pavements, PCC surface texture techniques) that may yet prove effective. Tests to determine the susceptibility of aggregate sources to stud wear are generally not reliable; however, the Micro-Deval test seems to be the most favorably rated. The WSDOT current practice of designing in an extra inch of pavement to account for future thickness loss associated with diamond grinding is sound policy and should be continued. As more PCC pavement in Washington State is due for replacement, WSDOT should consider a hardness specification program like Alaska’s in order to prevent the use of stud wear-susceptible aggregate sources.