SAN FRANCISCO (KRON) -Officials deemed it necessary to close the northbound lanes of the Golden Gate Bridge during the San Francisco Marathon because of terrorism concerns.

This is the first time the city will shut down part of the highway.

The lanes will be closed Sunday between 6 to 9 a.m. 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.

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