SAN FRANCISCO (CBS SF) — A six-year, $1 billion construction project at the north end of San Francisco will finally unleash traffic going to and from the Golden Gate Bridge along Doyle Drive, but not without one more major road closure and detour.

The final phase of the Doyle Drive replacement stretches from the Marina along Crissy Field to the bridge.

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Thousands of tons of gravel, and miles of rebar have gone into the structure, and countless dirt movers and operators have reworked the landscape.

Traffic that has been going in both directions in one new tunnel for three years will finally spread out.

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“Right now everybody’s really squeezed in a tight configuration with no shoulders,” said Molly Graham, project spokeswoman.

Soon after Memorial Day, contractors plan one last big road closure as the major construction is completed.  The closure is expected to last three days, beginning on a Thursday night at 10 p.m.

When the roadway reopens, every detour will go away, and closed ramps will be back in use for drivers.

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“All the connections from Highway 1 will be open, and then rather than having north and southbound traffic on this one single bridge over here, this bridge will carry northbound traffic, and the other bridge will only be southbound,” Graham said.