A year ago this week a movable median barrier was placed on the Golden Gate Bridge, an act that has made the span much safer, officials say.

It has already paid dividends, preventing at least four potential head-on collisions, they said.

“And unlike a lot of the changes we make at the bridge, by about the second day no one was talking about it,” said Kary Witt, bridge manager. “It fit right in almost like it had always been here.”

Of course it had not.

Until early January 2015, the freeway-speed traffic on the bridge was separated only by small, yellow tubes sticking up between lanes. Workers on a truck placed those rubber, 19-inch-high tubes by hand on the roadway every 25 feet to separate traffic.

Now yellow “zipper” trucks move a 1-foot-wide, 32-inch-high barrier made of high-density concrete clad in steel that is tightly pinned together that form a semi-rigid structure. The median is 13,340 feet, with each of its blocks weighing 1,500 pounds. It takes about 30 minutes to move from one side of the span to the other.

“It’s done what it was supposed to do: keep people from harm,” said Priya Clemens, bridge spokeswoman.

Between 1970 and last January there were 128 head-on collisions on the span, 16 fatalities and dozens of serious injuries.

“We know for sure that without the barrier, cars would have crossed over into oncoming traffic,” Witt said.

The barrier rests on the bridge with gravity holding it in place, but is strong enough to absorb major impacts without moving because of an internal spring system. Since the installation of the $30 million project, bridge officials and the barrier’s manufacturer, Barriers Systems Inc., have run tests including running the zipper truck several times to help calibrate the barrier to create the proper amount of pressure between each unit.

Some of the harder collisions in the past year have displaced the barrier by up to a foot. Typically a bridge truck is sent out to straighten the barrier.

“It’s been able to withstand a big rig truck hitting it,” Witt said. “It’s done its job.”

Bridge officials have not seen ricochet crashes that some thought would occur with the hard median barrier in place. About 40 million cars cross the span each year.

In emergencies, the barrier can be opened in minutes to allow emergency crews through, although that has not occurred in the last year. What has occurred in less extreme circumstances is emergency crews coming from the opposite direction on the span and working across the barrier to render aid at an accident, Witt said.

Bridge officials are concerned the solid barrier has made it more comfortable for people to drive faster than the posted 45 mph speed limit.

“When the barrier went up people felt safer and we saw a dramatic increase in speeds,” Witt said. “When the CHP comes out, writing speeding tickets is like shooting fish in a barrel. People need to slow down. The lanes are narrow and there is little margin for error.” —— (c)2016 The Marin Independent Journal (Novato, Calif.) Visit The Marin Independent Journal (Novato, Calif.) at www.marinij.com Distributed by Tribune Content Agency, LLC. AMX-2016-01-14T00:01:00-05:00