Interstate 580 is Livermore's primary east-west six-lane freeway. I-580 passes the outskirts of Livermore before it heads east through the Altamont Pass to the Central Valley and Interstate 5. I-580 and I-5 are the main route of San Francisco Bay Area to Los Angeles truck shipping traffic. Interstate 680 lies about west of Livermore. Highway 84 heads southwest from I-580 to Fremont. Vasco Road, an unnumbered highway that is maintained by Alameda and Contra Costa counties, connects Livermore to Brentwood and the Sacramento-San Joaquin River Delta area.