SAN FRANCISCO » Golden Gate Bridge shut down to private vehicles early Saturday so workers can install a moveable median barrier designed to prevent head-on collisions, part of an effort to increase safety along the iconic structure, according to Lt. Hector Bough of bridge security.

Transit buses, emergency vehicles, pedestrians and bicyclists will be able to cross the bridge while the barrier is being installed, the Golden Gate Bridge Highway and Transportation District said. The bridge is scheduled to reopen to all traffic Monday at 4 a.m. PST

The weekend closure will be the longest in the bridge’s history and the first since 1987, when the bridge closed for a few hours for a celebration of the 50th anniversary of its construction.

Currently, small plastic tubes are all that separate vehicles traveling in opposite directions on the bridge.

They have done little to prevent crashes. Since 1970, there here have been 128 head-on collisions on the bridge, resulting in 16 deaths, Golden Gate Bridge spokeswoman Priya Clemens said.

To create a moveable barrier, 3,500 steel-clad concrete blocks attached together by steel pins will be installed through the weekend along the 1.7-mile-long bridge and on the approach portion of Highway 101 north of the Golden Gate.

To reconfigure the bridge’s six lanes during the rush-hour commute, the 32-inch-tall and 1-foot-wide barrier will be moved using trucks.

"The board of directors had been looking for a long time to find a way to prevent head-on collisions and enhance safety, but we didn’t have the money, and the technology didn’t exist," David Clemens said.