Georgia Highway 400 (always known locally as Georgia 400) is a highway in the U.S. state of Georgia that goes from Atlanta at I-85 to Buckhead, Sandy Springs, Roswell, Alpharetta, Forsyth County, Dawson County, and Dahlonega. Like the interstate highways, it is a limited access road (with exit ramps instead of intersections), but unlike the interstates (which were renumbered by the GDOT in 2000), the exit numbers do not indicate mileage: they still go up sequentially one-by-one. Once 400 passes exit 17 (S.R. 306), it changes from a limited access highway into an at-grade divided highway.

The southern section of Georgia 400 (from I-285 to I-85) was built last, and is currently the only toll road remaining in Georgia. Built in the 1990s, this section was fought bittery by residents, who eventually ended up having their homes and large parts on their neighborhoods destroyed for the construction. Many remaining residents now live on dead end streets with significant noise pollution. Existing exits were renumbered up by four to accommodate the extension, which has a single toll booth in the middle of its length, accepting change or cruise cards. There is also currently no way to go from 400 south to 85 north or vice versa, except by a confusing route via Sidney Marcus Boulevard.

At one time, Georgia 400 was to connect to Interstate 675 in DeKalb County; however, the locals did not want the highway to cut through their neighborhoods and had the idea killed.

Georgia State Toll Route 400/T. Harvey Mathis Parkway Interchanges and Exit Numbers

Buckhead

• I-85 South (S.R. 403 South)/Downtown Atlanta/Atlanta Airport to I-75 (S.R. 401)/Macon/Marietta/Chattanooga (no number)
• Sidney Marcus Boulevard to I-85 North (S.R. 403 North)/Greenville) (exit 1)
• Lenox Road West (S.R. 141 Connector West) to Piedmont Road (S.R. 237) (exit 2)
• Lenox Road East (S.R. 141 Connector East) to Peachtree Road (S.R. 141) (exit 2)

Sandy Springs

• Glenridge Connector West (S.R. 407 Loop West) to Johnson Ferry Road (exit 3)
• Glenridge Connector East (S.R. 407 Loop East) to Peacthree-Dunwoody Road (exit 3)
• Toll Plaza ($.50 per passenger vehcile) (no number)

Georgia State Route 400/United States Highway 19/Turner McDonald Parkway Interchanges and Exit Numbers

Sandy Springs

• I-285 East (S.R. 407 East)/Greenville/Augusta (exit 4A)
• I-285 West (S.R. 407 West)/Chattanooga/Birmingham (exit 4B)
• Abernathy Road/Dunwoody/Sandy Springs (exit 5) (Southbound)
• Abernathy Road East/Dunwoody (exit 5A) (Northbound)
• Abernathy Road West/Sandy Springs (exit 5B) (Northbound)
• North Springs Train Station/MARTA Parking (exit 5C) (Southbound)
• Northridge Road (exit 6)

Roswell

• Holcomb Bridge Road (S.R. 140)/Roswell/Norcross (exit 7) (Southbound)
• Holcomb Bridge Road East (S.R. 140 East)/Norcross (exit 7A) (Northbound)
• Holcomb Bridge Road West (S.R. 140 West)/Roswell (exit 7B) (Northbound)

Alpharetta

• Mansell Road (exit 8)
• Haynes Bridge Road (exit 9)
• Old Milton Parkway (S.R. 120) (exit 10)
• Windward Parkway (exit 11)

Forsyth County

• McFarland Road (exit 12)
• Peachtree Parkway (S.R. 141) (exit 13)
• Buford Highway East (S.R. 20 East)/Buford (exit 14)
• Buford Highway West (S.R 20 West)/Cumming (exit 14)
• Bald Ridge Marina Road/Bald Ridge Marina (exit 15)
• Pilgrim Mill Road/Lake Lanier (exit 16)
• Keith Bridge Road (S.R. 306)/Gainesville (exit 17)

Dawson County

• Dawsonville

Lumpkin County

• Dahlonega