Interstate 12 functions as a bypass route for I-10 north of Lake Pontchartrain and the New Orleans metropolitan area. Although an intrastate route, I-12 provides a significant role in cross-country travel.
The freeway splits with Interstate 10 in Baton Rouge as a busy commuter route through suburban areas east to Denham Springs. Continuing east, I-12 becomes more rural through areas of pine forest, but still with moderate traffic given it accommodates just four overall lanes.
Interstate 55 crosses paths with I-12 outside Hammond, the largest city between Baton Rouge and Slidell. The freeway passes south of the city street grid and quickly exits the area toward Covington and the Lake Pontchartrain North Shore communities of Madisonville and Mandeville. There U.S. 190 ties in from the north end of Lake Pontchartrain Causeway, a lengthy toll bridge leading south to Metairie and Jefferson Parish west of New Orleans.
The remainder of Interstate 12 leads east through St. Tammany Parish to Slidell and the junction with I-10 and I-59 north. The freeway passes through North Slidell and suburban areas before defaulting onto I-10 east across Pearl River Wildlife Management Area into Mississippi.
Parallel U.S. Routes
Interstate 12 replaced U.S. 190 as the through route north of Lake Pontchartrain. U.S. 190 parallels I-12 to the north from Baton Rouge east to Covington and to the south between Mandeville and Slidell.
Interstate 12 Extension
The Louisiana Statewide Transportation Plan Update in 2003 outlined a limited access highway looping northeast from I-10 west of Louisiana 415 in West Baton Rouge Parish near Port Allen to U.S. 190 and the Mississippi River Bridge. Named the Northern Baton Rouge Bypass, the corridor extended east from Scotlandville in Baton Rouge through Central and Denham Springs to Interstate 12 at Walker in Livingston Parish.1
The Northern Baton Rouge Bypass was listed as Megaproject Item LSTP-051 in the Louisiana Statewide Transportation Plan Update (December 2003). Megaprojects considered for construction were listed in the report under the first chapter. A southern bypass route was considered but was later removed from the plan due to the substantial environmental cost of building over sensitive lands. U.S. 190 between U.S. 165 and the Northern Baton Rouge Bypass, via Kinder, Eunice, Opelousas and Krotz Springs, was also being considered for upgrade to freeway standards as part of projects LSTP-056 and LSTP-057.1
The Northern Baton Rouge Bypass was planned as a future Interstate highway based on this excerpt from page C-1 of the Louisiana Statewide Transportation Plan Update report:1
Break out the Baton Rouge North Bypass from I-10 to I-12 (LSTP-051) to Priority A and B: Priority A – new Interstate I-12 from I-10 west of LA 415 to US 190 and bridge rehabilitation to Airline Highway, stop at Plank Road interchange. Move project from Priority B to Priority A ‘mega’ projects. Priority B – Plank Road interchange to I-12, build/upgrade to 4-lane interstate standards”.
Commissioned by the Capital Region Planning Commission (CRPC), a consultant study released on November 9, 2004 recommended the central route for the bypass. It would begin at Interstate 10 a few miles west of LA 415 in West Baton Rouge and connect with U.S. 190 just west of LA 1145. The bypass would then continue east along U.S. 190 across the Mississippi River and connect with U.S. 61 (Airline Highway) at Scotlandville, Baton Rouge. Northeasterly from there, the expressway would extend to a point a few thousand feet north of Hooper Road, then cross Blackwater, Sullivan, Hooper and Greenwell Springs Roads. Spanning the Amite River, the route would proceed east to LA 1026, Range Road, and LA 447 (Walker Road), then curve southeast to Interstate 12 between the Walker and Satsuma interchanges.2
The report recommendsed a six-phase approach for building the highway:
- Phase One – Plank Road east to LA 16 (Range Road), $263 million, open 2012
- Phase Two – LA 16 (Range Road) east to LA 447 (Walker North Road), $76 million, open 2014
- Phase Three – LA 447 (Walker North Road) east to Interstate 12, $87 million, open 2014
- Phase Four – Interstate 10 east to U.S. 190/LA 1, $93 million, open 2016
- Phase Five – upgrade U.S. 190 from Phase Four segment east to Mississippi River Bridge, $72 million, open 2018
- Phase Six – upgrade U.S. 190 Mississippi River Bridge and extend freeway through northern Baton Rouge along U.S. 61-190 east to Plank Road, $319 million, open 2020
The CRPC consultant study in 2004 indicated it would cost $910 million to construct the expressway. This included spending $300 million for upgrading the U.S. 190 Mississippi River Bridge, which was built in 1940. Due to the high costs for construction of the bypass, many believed that the road should be deferred in favor of improving existing roads around the Baton Rouge metropolitan area, especially Interstate 12 and main arteries serving Downtown. Furthermore, one of the project’s chief critics, State Representative William Daniel, a Democrat from Baton Rouge, sued the CRPC to get the information about the costs of the corridor prior to the official release date of the study. Coupled with an expected completion date in 2020 and the prospect of tolls, critics were also skeptic about the project’s viability.2 The Northern Baton Rouge Bypass never advanced beyond early studies and discussion.
According to the journal Roads and Bridges, the I-12 corridor should be extended westward:
Interstate 12 Houston to Austin: These metropolitan areas have grown rapidly. Less than 100 miles, this route would require upgrading from Austin to Interstate 10 along the state route 71 corridor.
SH 71 is a four-lane roadway for its entire length, with portions already upgraded to expressway standard. One upgrade along the SH 71 corridor is the SH 71 Express Project in Austin. Construction between early 2015 and late 2016 upgraded 3.9-miles of the highway, from Presidential Boulevard at AUS Airport to SH 130 near Onion Creek, to a limited access toll road. Work added two toll lane overpasses at FM 973 and SH 130.
- East End – Slidell, LA
- West End – Baton Rouge, LA
- Branch Routes – 0
- Mileage – 85.59
Cities – Baton Rouge, Denham Springs, Walker, Hammond, Covington, Slidell
- Junctions –
Source: December 31, 2018 Interstate Route Log and Finders List
I-12 Annual Average Daily Traffic (AADT)
Source: LADOTD Estimated Annual Average Daily Traffic Routine Traffic Counts
2017 – East Baton Rouge 2015 Livingston 2016 Tangipahoa 2015 St. Tamminy
* – AADT between Exits 6 to 7 recorded in 2014
The 1963 Louisiana Official Highway Map shows the westernmost two miles of I-12 as complete. This was shown correctly as under construction on the Baton Rouge inset.
Work was also underway after 1963 on I-12 from LA 447 and the Ponchatoula Bypass, the first portion of I-55 opened to traffic in Louisiana.
Interstate 12 was open from Baton Rouge east to U.S. 51 Business at Hammond by 1972.
Construction along I-12 continued in 1972 on the easternmost segment from LA 434 to I-10 and 59.
Interstate 12 was completed between U.S. 61 (Airline Highway) at Baton Rouge and I-55 at Hammond in 1969. The western most two miles of I-12 opened in conjunction with Interstate 10 east from College Drive in 1965.3 Interstate 10 southeast from I-12 would not be completed until 1974, resulting in traffic defaulting from I-10 east onto I-12 and U.S. 61 until 1969.
In 1993, the Louisiana State Legislature passed a resolution declaring Interstate 12 the West Florida Republic Parkway. This name stems from the 74 day West Florida Republic existence that occurred between an 1810 revolt against Spain and the forced annexation of the eight parishes into the Louisiana Purchase by the United States. During mid-November of 2003, signs were installed proclaiming the highway the West Florida Republic Parkway.4
East End – Slidell
East End Throwback
West End – Baton Rouge
West End Throwback
- Louisiana Statewide Transportation Plan Update.
- “Bypass report shows $910 million, 6-phase plan.” Baton Rouge Advocate (LA), October 26, 2004.
- “Booklet for I-10 Dedication Ceremony.” Baton Rouge Digital Archive, September 18, 1964.
- “Signs on I-12 remind people of Florida Parishes republic.” Fox 8 Live WVUE-TV New Orleans, November 24, 2003.
- “I-10 welcome center reopens near Slidell.” The Times-Picayune, June 29, 2009.
Page updated January 22, 2020.