 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 the busiest section of the highway was the expressway between SR 171 and Stratford Road in Moses Lake, serving an average of 19,000 vehicles, while the least busiest section of the highway was between SR 172 in Sims Corner and SR 174 in Leahy, serving an average of 570 vehicles. SR 17 between Mesa and the Moses Lake area is designated as part of the National Highway System, which includes roadways important to the national economy, defense, and mobility; and as part of WSDOT's Highways of Statewide Significance, which includes highways that connect major communities in the state of Washington.
