SR 126 ends where the Emerson Expressway becomes a divided freeway.

(Emerson Street continues east as a city street to Spring Glen Road just south of US 90 (Beach Boulevard; SR 212).

The rest of the Emerson Expressway is the unsigned 0.930-mile-long (1.497 km) State Road 228A (SR 228A), traveling roughly north from the end of SR 126 to a merge with SR 228 (Hart Bridge Expressway).

SR 126/Emerson Street is the only non-freeway section of US 1 Alt., which bypasses Downtown Jacksonville to the east via the Hart Bridge.

The entire route is in Jacksonville, Duval County.