SAN FRANCISCO (CBS SF) — Work has begun to bring major changes to Van Ness Avenue in San Francisco.

Work began Friday night to reconfigure southbound Van Ness at Broadway to allow two dedicated left turn lanes and two southbound lanes.

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Over the weekend, left turn lanes from Van Ness at most intersections will be permanently removed.

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Southbound Van Ness at Broadway and northbound Van Ness at Lombard will keep the left turns.

Once left turns have been removed, work on the median will begin, which will reduce the number of traffic lanes from three to two in each direction beginning Monday. The median will be rebuilt at the end of construction.

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Drivers are encouraged to allow for extra travel time and to test new routes before these changes take effect.