State Route 84 (SR 84) is a split-section California State Highway consisting of two sections. The first section is an east–west arterial road running from San Gregorio to Menlo Park, across the Dumbarton Bridge through Fremont and Newark  and ending at I-580 in Livermore. The route overlaps the freeway segment of U.S. 101 between Woodside Road in Redwood City and Marsh Road in Menlo Park. The segment between Marsh Road and the Dumbarton Bridge has been upgraded to an expressway and is known as the Bayfront Expressway. The segment from the eastern end of the Dumbarton Bridge to the interchange with I-880 has been upgraded to a freeway.