 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 average annual daily traffic ( AADT ) , which is a measure of traffic volume for any average day of the year . In 2011 , WSDOT calculated that between 8 @,@ 200 and 26 @,@ 000 vehicles per day used the highway , mostly within Battle Ground . The entire route is designated as part of the National Highway System , which includes roadways important to the national economy , defense , and mobility . 
