It runs 35.71 miles (57.47 km) in a north–south direction from the junction of Interstate 20 (I-20), U.S. Highway 71 (US 71), and LA 72 in Bossier City to the Arkansas state line north of Plain Dealing.

Opposite this intersection are ramps leading to a partial interchange with I-20 and US 71 at the point where the two highways begin a concurrency across the Red River westward into Shreveport.

[2][3][4] From this intersection, LA 3 proceeds north along Benton Spur, an undivided four-lane thoroughfare with a center turning lane, and continues onto an overpass across the Kansas City Southern Railway (KCS) tracks.

LA 3 continues northward and enters an interchange with I-220 (exit 11), a northern bypass of Shreveport that connects to I-20 westbound toward Dallas, Texas and eastbound toward Monroe.

Over the next 7.0 miles (11.3 km), LA 3 continues northward, closely following the Union Pacific Railroad (UP) tracks through points such as Vanceville and Willow Chute, before entering Benton, the seat of Bossier Parish.

[11] This overpass was constructed on the west side of the existing at-grade crossing of the Kansas City Southern Railway which was formerly a source of traffic congestion on Benton Road.

The route was added in 1966 when LA 3 was slightly re-routed to connect with the ramps to the newly-constructed section of I-20 between the Red River Bridge at Traffic Street and US 71 at Barksdale Boulevard.