Studded Tires
Here is some information and links on Studded Tires from a recent Section meeting presentation by Howard Hamby.
http://www.crab.wa.gov/LIBRARYData/REPORTS/State/081201PavementsStuddedTiresFinalv2.pdf
http://www.wsdot.wa.gov/research/reports/fullreports/471.1.pdf