SAN FRANCISCO — For the first time, northbound lanes of the Golden Gate Bridge will be closed during the San Francisco Marathon because of terrorism concerns.

The Marin Independent Journal reports (http://bayareane.ws/2uM4NMo) bridge operators decided to keep motorists out of those lanes between 6 to 9 a.m. Sunday after several terrorist attacks elsewhere occurred where drivers intentionally plowed into pedestrians.

Southbound lanes will be kept open because runners are protected from southbound vehicles by a steel-and-concrete median barrier.

About 4,500 vehicles typically use the northbound lanes during those hours. Bridge operators say only Golden Gate Transit buses and emergency vehicles can go northbound, but other motorists will have to use alternate bridges to get to Marin and the North Coast.

Since the Sept. 11 attacks, more than $15 million has been spent to improve security on the bridge.