From the northwest, LA 3040 begins at an intersection with LA 24 in Bayou Cane. It turns south and then southeast, running through Bayou Cane as Martin Luther King Boulevard. Intersecting with South Hollywood Road (formerly LA 3040 Spur), the local name changes to West Tunnel Boulevard. At LA 661 (St. Charles Street), LA 3040 enters Houma and begins to head in a more easterly direction. At Naquin Street, LA 3040 divides to follow a pair of one-way streets, Honduras Street eastbound and Bond Street westbound. In this configuration it intersects LA 312 (Lafayette Street) and LA 182 (Barrow Street). LA 3040 converges four blocks east of LA 182 and continues through the Houma Tunnel under the Gulf Intracoastal Waterway. On the other side, LA 3040 continues as Tunnel Boulevard, turns northeast, and intersects LA 57 (Grand Caillou Road) before ending at LA 661 (Howard Avenue).
LA 3040 is an undivided, five-lane highway (with middle turning lane) from LA 24 to South Hollywood Road (former LA 3040 Spur). It then widens to a divided, four-lane highway to the Houma Tunnel where it narrows to an undivided, two-lane highway. On the east side of the tunnel, it widens again to a divided, four-lane highway for the remainder of its route.