Interstate 12 (I-12) is an Interstate Highway located entirely within the U.S. state of Louisiana. It spans a total of 86.65 miles (139.45 km) in an east–west direction from I-10 in Baton Rouge to an interchange with both I-10 and I-59 in Slidell. Along the way, it passes through the city of Hammond, where it intersects I-55 and US 51. It also serves the smaller cities of Denham Springs and Ponchatoula, as well as the St. Tammany Parish cities of Covington and Mandeville. Skirting the northern shore of Lake Pontchartrain, I-12 serves as a northern bypass of the New Orleans metropolitan area and as an alternate route for I-10, which serves the city of New Orleans itself.
U.S. Highway 171 (US 171) is a part of the United States Numbered Highway System and the only route within that system currently located entirely within the state of Louisiana. It spans 177.44 miles (285.56 km) in a north–south direction from the junction of US 90 and Louisiana Highway 14 (LA 14) in Lake Charles to the junction of US 79/US 80 and LA 3094 in Shreveport.
U.S. Route 190 (US 190) is an east–west United States Highway in Louisiana and Texas. Segments of US 190 will be upgraded to Interstate 14 (I-14), the first 24.8-mile (39.9 km) segment was opened on January 26, 2017.
Airline Highway is a divided highway in the U.S. state of Louisiana, built in stages between 1925 and 1953 to bypass the older Jefferson Highway. It runs 115.6 miles (186.0 km), carrying U.S. Highway 61 from New Orleans northwest to Baton Rouge and U.S. Highway 190 from Baton Rouge west over the Mississippi River on the Huey P. Long Bridge. US 190 continues west towards Opelousas on an extension built at roughly the same time.
Louisiana Highway 10 (LA 10) is a state highway located in southern Louisiana. It runs 255.51 miles (411.20 km) in an east–west direction from U.S. Highway 171 (US 171) south of Leesville to the Mississippi state line east of Bogalusa.
Louisiana Highway 6 (LA 6) is a state highway located in western central Louisiana. It runs 54.52 miles (87.74 km) in an east–west direction from the Texas state line southwest of Many to U.S. Highway 71 (US 71) and U.S. Highway 84 (US 84) in Clarence.
Louisiana Highway 81 (LA 81) is a state highway located in Pointe Coupee Parish, Louisiana. It runs 8.82 miles (14.19 km) in a generally north–south direction from LA 77 in Livonia to a second junction with LA 77 in Fordoche.
Louisiana Highway 78 (LA 78) is a state highway located in Pointe Coupee Parish, Louisiana. It runs 7.55 miles (12.15 km) in a north–south direction from a junction with U.S. Highway 190 (US 190) and LA 411 in Livonia to LA 1 in Parlange.
U.S. Highway 51 (US 51) is a part of the United States Numbered Highway System that spans 1,277 miles (2,055 km) from LaPlace, Louisiana to a point north of Hurley, Wisconsin. Within the state of Louisiana, the highway travels 69.12 miles (111.24 km) from the national southern terminus at US 61 in LaPlace to the Mississippi state line north of Kentwood.
Louisiana Highway 123 (LA 123) is a state highway located in Grant Parish, Louisiana. It runs 15.95 miles (25.67 km) in a southwest to northeast direction from LA 8 east of Colfax to US 165 east of Breezy Hill. The signage for LA 123 carries east–west directional banners unlike most odd numbered state highways in the primary range, which are bannered north–south.
Louisiana Highway 64 (LA 64) is a state highway located in southeastern Louisiana. It runs 20.45 miles (32.91 km) in a general east–west direction from LA 964 in Zachary to the junction of LA 16 and LA 1026 north of Denham Springs.
U.S. Highway 61/190 Business is a state highway in Louisiana that serves East Baton Rouge Parish. It spans 10.89 miles (17.53 km) in a southeast to northwest direction and it is bannered as Business 61/190, with no directional shields. It generally follows the 1940s-1950s alignment of US 61/190 through Baton Rouge.
Louisiana Highway 103 is a state highway located in St. Landry Parish that spans 39.5 miles (63.6 km) in a wide semi-circle around the north side of Opelousas. The route is not bannered but runs in an overall west–east direction from U.S. Highway 190 near Lawtell to LA 31 in Leonville. Along the way, it passes through the towns of Washington and Port Barre.
Louisiana State Route 7 was one of the 98 original state highways that were established in 1924. It was split into two separate segments, with the western section running in a west to east direction for 110.80 miles (178.32 km), spanning from Deweyville to the Atchafalaya River. The eastern section ran for 144.50 miles (232.55 km) from Lottie to the Mississippi state line, in a west to east direction.
