[1] In the more rural parts of LA 18's span, it is commonly referred to as River Road, but it becomes 4th Street once it enters Westwego.

At Bridge City, LA 18 leaves the river and briefly merges with U.S. Highway 90 northbound, then turns east along Seven Oaks Blvd.

LA 18 then goes south and ends at the intersection of Lafayette St. and the Westbank Expressway.

(One notable exception is that LA 18 is routed along Louisiana Street rather than the parallel Sala Avenue through Westwego's historic district.)

LA 18 Spur continues southward for 0.6 miles (0.97 km)[1] on Louisiana Street until it meets the Westbank Expressway (U.S. 90 Business).