SR 520 begins in Seattle at I-5 and continues east across Lake Washington on the Evergreen Point Bridge through Bellevue, interchanges with I-405, then turns northeast, passes the main Microsoft campus (which funded an overpass at NE 36th St and an interchange at NE 40th to supplement the existing interchange at NE 51st St), and terminates in Redmond at SR 202. The section between I-5 and Bellevue Way was opened in 1963, with the interchange at I-405 built in 1966. It was further extended to it current terminus between 1973 and 1982. The Washington State Department of Transportation is currently widening the freeway on the Eastside, modifying interchanges, and moving the HOV lanes to the inside of the roadway.