Every year, the Washington State Department of Transportation (WSDOT) conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of annual average daily traffic (AADT), which is a measure of traffic volume for any average day of the year. In 2011, WSDOT calculated that between 850 and 1,100 vehicles per day used the highway, mostly at the US 12 intersection in Mossyrock.[4]
History
SR 122 between Silver Creek and Harmony follows the route of an unpaved road built in the 1910s and removed after the completion of the Mayfield Dam in 1963,[5][6] while the road from Harmony to Mossyrock was built in the 1940s.[7] The roadway was later reconstructed and designated in 1991 as SR 122, a number previously used on the route of SR 142 until 1967.[2]