The county is traversed by three Interstate Highways and one U.S. Highway, as well as an additional freeway and one major expressway. US-89 enters from Davis County to the north and traverses the county arrow-straight until merging with I-15 in north Draper. It is known as State Street along most of the route and is the primary surface road in the valley. I-15 and I-80 intersect just west of Downtown Salt Lake City, merging for approximately north-to-south. I-80 continues west past the Salt Lake City International Airport and east through Parley's Canyon and into the Wasatch Range. I-15 traverses the valley north-to-south, providing access to the entire urban corridor. The freeway is 10–12 lanes wide after a major expansion project from 1998 to 2001 undertaken in preparation for the 2002 Winter Olympics. I-215 directly serves many of the suburbs of Salt Lake City in the western, central, and eastern portions of the valley in a 270° loop. SR-201, alternatively known as the "21st South Freeway", provides access to West Valley City and the west side of the valley. Bangerter Highway (SR-154) is an expressway that traverses the entire western end of the valley from the airport, ending at I-15 in southern Draper. SR-68, or Redwood Road, is the only surface street that traverses the entire valley from north-to-south. The Legacy Parkway opened in 2008 to connect with I-215 at the north end of the valley, providing an alternative route into Davis County to alleviate congestion. The Mountain View Corridor is a limited-access highway across the SW part of the county; construction began in 2010 and it was put into operation in stages.