between Oakland and San Francisco. Prior to the bridges and, later, the Transbay Tube, transbay transportation was dominated by fleets of ferryboats operated by the Southern Pacific Railroad and the Key System transit company. However, in recent decades, ferries have returned, primarily serving commuters from Marin County, relieving the traffic bottleneck of the Golden Gate Bridge. (See article Ferries of San Francisco Bay). The bay also continues to serve as a major seaport. The Port of Oakland is one of the largest cargo ports in the United States, while the Port of Richmond and the Port of San Francisco provide smaller services. An additional crossing south of the Bay Bridge has long been proposed. Recreation San Francisco Bay is a mecca for sailors (boats, as well as windsurfing and kitesurfing), due to consistent strong westerly/northwesterly thermally-generated winds – Beaufort force 6 () is common on summer afternoons – and protection from large open ocean swells. Yachting and yacht racing are popular pastimes and the San Francisco Bay Area is home to many of the world's top sailors. A shoreline bicycle and pedestrian trail known as the San Francisco Bay Trail encircles the edge of the bay. The San Francisco Bay Area Water Trail, a growing network of launching and landing sites around the Bay for non-motorized small boat users (such as kayakers) is being developed. Parks and protected areas around the bay include Eden Landing Ecological Reserve, Hayward Regional Shoreline, Don Edwards San Francisco Bay National Wildlife Refuge, Hayward Shoreline Interpretive Center, Crown Memorial State Beach, Eastshore State Park, Point Isabel Regional Shoreline, Brooks Island Regional Shoreline, and César Chávez Park. The California Office of Environmental Health Hazard Assessment (OEHHA) has developed a safe eating advisory for fish caught in the San Francisco Bay based on levels of mercury or PCBs found in local species. The San Francisco Bay Area Water Trail is a planned system of designated trailheads designed to improve non-motorized small boat access to the bay. The California Coastal Conservancy approved funding in March 2011 to begin implementation of the water trail. Gallery See also Golden Gate Golden Gate Bridge Hydrography of the San Francisco Bay Area Islands of San Francisco Bay J.C. Barthel, who prepared "plans for the docks and other water-front improvements in the San Francisco Bay district" McLaughlin Eastshore State Park Mount Diablo Mount Tamalpais State Park Napa Sonoma Marsh Point Pinole Regional Shoreline,