 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 2013, WSDOT calculated that the busiest section of US 2 within Washington was the Hewitt Avenue Trestle above the Snohomish River east of Everett, carrying over 76,000 vehicles, while the least busiest section of US 2 is in Moses Coulee, carrying 630 vehicles.The entire route of US 2 within Washington is designated as part of the National Highway System, classifying it as important to the national economy, defense, and mobility.