SR 124 begins at an
intersection with
I-20/
US 278/
SR 12 in
Lithonia, in DeKalb County. To the northeast, it crosses into Gwinnett County and, immediately, crosses over the
Yellow River. Southwest of
Snellville, it meets
SR 264. Through Snellville north to
Lawrenceville, the road is known as
Scenic Highway. In town, it intersects
US 78/
SR 10 and then, the
Ronald Reagan Parkway; the Eastside Medical Center, Snellville's largest employer, is located on this portion of the route. On the southwestern edge of Lawrenceville is
Sugarloaf Parkway. Farther into town, it intersects
SR 20. Then,
US 29/
SR 8 join the road in a
concurrency to the west. A short distance later, SR 124 splits to the north, and almost immediately, joins SR 20 concurrently to an
interchange with
SR 316 (University Parkway). A short distance later, SR 124 splits off to the northeast. From here until SR 211(Old Winder Highway, also about where Braselton Town Limits begin), the road name is changed to Braselton Highway. Northwest of
Dacula, it meets
SR 324, passes by
Mill Creek High School a couple miles later, and crosses into Barrow County shortly thereafter. After an intersection with
SR 211, it enters Jackson County. A few miles later is
Braselton. There, it meets
SR 53. Between SR 211 and SR 53, the signed direction of the highway changes from north to east (and west to south in the opposite direction) It curves to the southeast to
SR 332. The road heads westerly until it meets its northeastern terminus, an intersection with
SR 11 in the southwestern part of
Jefferson. SR 124 from SR 324 to its eastern terminus at SR 11 runs parallel to, but does not have an interchange with,
Interstate 85. However, travelers can access I-85 from SR 124 via SR 324, Hamilton Mill Parkway, SR 211, and SR 53. ==Major intersections==