A car drives along a wide divided highway bordered by trees, with an exit sign on the right shoulder. — File image used in North Atlanta Star’s Georgia 400 coverage; not a view of the December 13 lane closure.

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Drivers who use the northbound Georgia 400 flex lane approaching Windward Parkway will lose that extra rush-hour space beginning Sunday, Dec. 13.

The permanent closure covers approximately three-quarters of a mile, from just south of the Webb Bridge Road overpass to Exit 11 at Windward Parkway. Weather permitting, contractors will remove the flex-lane signs and striping and install a temporary concrete barrier as construction advances on the Georgia 400 express-lanes project.

Four regular northbound lanes will remain open. Drivers taking Exit 11 will still reach Windward Parkway through the two-lane exit ramp on the right, while through traffic will continue in the main lanes, as outlined in the Alpharetta construction update.

The closing marks a visible change in a corridor where drivers have relied on shoulder lanes during peak traffic for more than a decade. Georgia DOT extended northbound flex-lane service from Old Milton Parkway to Windward Parkway in June 2015 as a relatively quick, low-cost way to add rush-hour capacity. The shoulder operated as an additional travel lane during designated morning and afternoon periods, with a 45 mph advisory speed.

That temporary congestion measure is now giving way to a much larger project. As North Atlanta Star explained in September, Georgia 400 is being widened for optional toll lanes between North Springs MARTA station and a point just north of McFarland Parkway in South Forsyth.

Plans call for two express lanes in each direction between North Springs and McGinnis Ferry Road, then one in each direction through the northern end of the corridor. The existing general-purpose lanes will remain free.

The Georgia DOT project schedule anticipates completion in 2031. Construction is already underway at several points between Sandy Springs and South Forsyth, with daytime work, overnight lane closures and traffic shifts expected as crews build drainage systems, retaining walls, bridges and new roadway connections.

For Alpharetta commuters, Dec. 13 will be the practical dividing line: the familiar shoulder lane approaching Windward will no longer open during busy periods. The four permanent northbound lanes and the Windward exit remain, but drivers who previously moved into the flex lane should allow extra time while traffic settles into the new pattern.

Drivers can check Georgia 511 before leaving, particularly for overnight closures that may affect the following morning’s commute.