A private consortium will build and operate toll lanes on GA-400 for 55 years under a deal that reshapes the daily commute for Alpharetta and Milton drivers.

State officials defended the public-private partnership (P3) model behind the SR 400 Express Lanes project on Monday, Sept. 21, as first reported by WSB-TV. The Georgia Department of Transportation (GDOT) and the State Road and Tollway Authority (SRTA) said the arrangement lets the state deliver infrastructure it could not fund with tax dollars alone.

The project will add two express lanes in each direction along 16 miles of GA-400, from the North Springs MARTA Station to McFarland Parkway in Milton. Construction began in April 2026 and is projected for completion in 2031.

Tim Matthews, director of GDOT's P3 division, told WSB-TV the model stretches limited state dollars. "We get more than we can afford when we go that way," Matthews said.

Under the agreement, a consortium called SR 400 Peach Partners will design, build, operate and maintain the lanes over the 55-year term, according to the AASHTO Journal. The consortium includes international firms Acciona Concessions, ACS Infrastructure and Meridiam. A $3.89 billion federal loan through the Transportation Infrastructure Finance and Innovation Act (TIFIA) program backs the project.

The consortium also paid GDOT a $3.8 billion concession fee the state can direct to other road projects, Construction Dive reported. That fee drew pointed criticism from Robert Poole of the Reason Foundation, a transportation policy group. In a June 2026 commentary, Poole wrote that the cost "will eventually be borne by customers who pay tolls," calling a concession fee on a new toll project "a recipe for considerably higher tolls."

Tolls will be set dynamically. When express-lane traffic drops below 45 miles per hour, the operator can raise rates to manage congestion, WSB-TV reported. A formula tied to Georgia economic data will allow the toll cap to adjust with inflation.

SRTA Chief Communications Officer Ericka Bayonne told WSB-TV the contract includes protections for drivers who depend on the corridor. State officials also pointed to more than 1.7 million free trips completed by buses and carpools on existing Georgia express lanes in 2025.

The groundbreaking ceremony drew nearly 300 stakeholders in April, according to True North 400, the community improvement district serving the GA-400 commercial corridor. The City of Alpharetta warned residents on March 23 to expect work zones and traffic shifts between McGinnis Ferry Road and McFarland Parkway.

GDOT plans to select a developer for a similar P3 project on the east side of I-285 in October.