Southern segment SR 115 runs north as
Southside Boulevard from its terminus at
US 1, providing access to
The Avenues. Right afterwards, the road goes through the largely residential and commercial south side of
Jacksonville with crossings at Baymeadows Road (
SR 152), Butler Boulevard (
SR 202),
Beach Boulevard (
US 90), and
Atlantic Boulevard (
SR 10). At the Southside Connector (
SR 113), SR 115 turns sharply to become the
Arlington Expressway, heading west into downtown via the
Mathews Bridge, where it turns north, becoming the
Martin Luther King Jr. Parkway (former Haines Street Expressway), and again turning to the west along with the MLK Parkway (now the former 20th Street Expressway), before reaching
I-95. The portion of the MLK Parkway is signed only as
US 1 Alt. and
US 1, not SR 115. The southern segment serves primarily as a conduit between the residential neighborhoods of
Southside and the commercialized areas farther north and downtown. Heavy traffic is commonplace along most of the road. To improve traffic flow, especially during rush-hours, in 2023 the
FDOT installed Florida's first double median U-turn intersection at the interchange with Beach Blvd. (US 90). In 2024 it also completed a major redesign of the intersection just north of the
cloverleaf interchange with SR 202 (Butler Boulevard expressway) and in the same year began reconstructing the intersection just south of the interchange. The new intersections' designs replace some of the left turn movements with
Michigan left turns in order to reduce the number of traffic light phases.
Northern segment Approximately two miles of SR 115 run unsigned along I-95. The second section of signed road runs from the junction of I-95 and Norwood Avenue (
SR 117) through northwest Jacksonville, passing through the Lake Forest section of the city before crossing a bridge over the
Ribault River, where it enters Riverview and then crosses another bridge over the
Trout River into the eastern edge of the College Park neighborhood, before entering the Garden City neighborhood at the intersection with
Florida State Road 104. FL 115 continues through Garden City, until the interchange with
I-295 and runs between the Forest Trails and the territory near the
Jacksonville International Airport before crossing a bridge over the Thomas Creek where it crosses the Duval-Nassau County Line, and ending at New Kings Rd (
US 1/
US 23) in
Callahan. The northern segment has the same function as the southern, except that it is built to lower standards and carries traffic south from the densely populated areas northwest of downtown into the heart of the city. Northbound, it is also an alternative to US 1/US 23 as a route to Callahan. ==Exit list==