SAN FRANCISCO (AP) — Oil tankers and other large vessels will be restricted from sailing beneath the San Francisco-Oakland Bay Bridge in dense fog under new rules shipping officials passed Thursday.

The San Francisco Bay Harbor Safety Committee passed the new guidelines five weeks after an empty oil tanker, the Overseas Reymar, sideswiped one of the span's towers and caused $3 million damage,.

Five years earlier, the 901-foot cargo vessel Cosco Busan hit a bridge tower and spilled 53,000 gallons of bunker fuel into the bay.

Both collisions occurred in foggy conditions with visibility of roughly a quarter mile.

"We were responding to the casualty of the Overseas Reymar," said Cynthia Stowe, the Coast Guard's captain of the Port of San Francisco. "We're taking a very conservative approach."

Thousands of oil tankers, cargo vessels and other ships sail in and out of San Francisco Bay annually.

Large oil spills could devastate myriad bird and animal species; the Cosco Busan spill killed 6,000 birds and fouled 69 miles of shoreline and beach.

Under the new rules, ships larger than 1,600 gross tons are restricted from sailing under the bridge when visibility is less than half a mile.

The rules only apply to ships sailing out of the bay, not to those coming in, because of concerns the limits would dampen commerce.

Still, environmentalists believe the limits were worthwhile.

"It should help reduce the risk of oil spills," said Deb Self, executive director of Baykeeper, a conservation group.