[2] The route has a spur that travels 0.64 miles (1.03 km) along Donohue Ferry Road from LA 3100 to Expressway Drive.

LA 3100 is an undivided two-lane highway with a center turning lane for its entire length.

LA 3100 was added to the state highway system in 1964, creating a state-maintained connection between the new Pineville Expressway and US 165 Bus.

Louisiana Highway 3102 (LA 3102) runs 9.33 miles (15.02 km) from Larto to Argo in Catahoula Parish.

Louisiana Highway 3103 (LA 3103) ran 0.8 miles (1.3 km) in an east–west direction, looping off of US 84 in Mansfield, DeSoto Parish.

From the west, LA 3103 headed northeast on Kings Highway past Mansfield High School, then curved due east onto McEnery Street.

Louisiana Highway 3105 (LA 3105) runs 6.21 miles (9.99 km) in a north–south direction from Arthur Ray Teague Parkway to the end of state maintenance at the northern boundary of the Bossier City city limits in Bossier Parish.

It crosses the Kansas City Southern railroad tracks, curving to the north-northwest and intersecting LA 72.

It spanned a total of 1.7 miles (2.7 km) along the present route of U.S. 190 on the north side of Covington.

[17] The route heads northeast from LA 75, which follows the east bank levee of the Mississippi River, and passes a series of industrial facilities in an otherwise rural area within the St. Gabriel city limits.

Louisiana Highway 3118 (LA 3118) runs 1.26 miles (2.03 km) in Fort Jesup, Sabine Parish.

It was the main route connecting Donaldsonville with the Sunshine Bridge across the Mississippi River until LA 3089 was re-routed and extended directly into town in the mid-1970s.

[21] The route has a spur that travels 0.07 miles (0.11 km) from LA 3121 to a dead end at the village's abandoned school property.

Near the end of its route, it passes through the adjacent unincorporated communities of Lutcher and Gramercy, terminating just south of a junction with US 61 (Airline Highway).

[28] The route served as a bypass of the downtown area and developed as a modern commercial corridor for the small city.

The construction of the nearby John James Audubon Bridge over the Mississippi River led to a reconfiguration of highway routes in the area.

It runs 10.25 miles (16.50 km) in a general east–west direction from the junction of Interstates 20 and 220 to LA 523, serving as a southwestern bypass of the downtown area.

With I-220, the highway helps to carry through traffic between the two disconnected portions of Interstate 49 (I-49), the area's main north–south route.

It spans 7.2 miles (11.6 km) in a north-south direction[29] along Leo Kerner/Lafitte Parkway between Jean Lafitte and Estelle (south of Marrero) and acts as a four-lane bypass to the older Barataria Boulevard (LA 45).

[33] The route connects Killona with LA 3127, a highway constructed in the 1970s that bypasses the various communities along the west bank of the Mississippi River between Luling and Donaldsonville.

[34] The route connects the industrial area of Taft with LA 3127, a highway constructed in the 1970s that bypasses the various communities along the west bank of the Mississippi River between Luling and Donaldsonville.

The Dow Chemical Company and Waterford 3 nuclear power plant are among the facilities served by the highway.

[36] The route heads north from LA 28 and passes through a wooded area of mixed residential and commercial establishments.

After curving due west, LA 3144 passes through a diamond interchange with US 167 (Pineville Expressway).

The Violet Canal bridge and extension of Judge Perez Drive to Poydras was opened in 1981,[39] and LA 3146 was deleted sometime afterward.

Louisiana Highway 3149 (LA 3149) runs 3.62 miles (5.83 km) from Mamou to Reddell in Evangeline Parish.