 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 2009, WSDOT calculated that as few as 4,400 cars traveled over the highway at the eastern terminus at SR 7, and as many as 8,600 cars at the western terminus at SR 507.The roadway linking McKenna to now SR 7 has existed since at least 1931, then designated State Highway 10, and by 1939 the highway designation had been changed to Secondary State Highway 5J (SSH 5J).