Interstate 12 (I-12): Louisiana Route, Length, Bridges and Crash Deaths

How long is I-12?

The FHWA Route Log lists I-12 at 86.65 miles, all of it in Louisiana. Wikipedia and Interstate Guide both use 85.59 miles, a little over a mile less.

The Route Log shows no stretch of I-12 shared with another Interstate, so an overlap cannot explain the 1.06-mile gap. Neither source says where the difference comes from.

Where I-12 starts and ends

I-12 begins at the I-10/I-12 split, exit 1A, about three miles east of downtown Baton Rouge in East Baton Rouge Parish. It ends at the northeast corner of Slidell, where it meets I-10 again and I-59 begins.

In between it crosses four parishes: East Baton Rouge, Livingston, Tangipahoa and St. Tammany. Denham Springs, Walker, Albany, Hammond, Ponchatoula, Robert, Madisonville, Covington, Mandeville and Lacombe all sit along the way. US 190 still parallels the Interstate, which took over as the through route north of the lake. Wikipedia puts the savings at about 22 miles for a Baton Rouge to Slidell trip compared with staying on I-10 through New Orleans.

Interstate junctions along I-12

Read from west to east, the list starts with I-10 and comes back to it near the end. I-12 leaves it at a three-wye interchange in Baton Rouge, crosses I-55 at exit 38 outside Hammond, and rejoins it at exit 85 in Slidell. That last interchange is also where I-59 starts its run north toward Picayune, Mississippi. Among the US highway exits, US 61 (Airline Highway) comes at exit 2, US 190 between Covington and Mandeville at exit 63 and US 11 in Slidell at exit 83.

Fatal crashes on I-12

Crashes on I-12 killed 99 people between 2020 and 2024. FARS records 93 fatal crashes over those five years, or close to 20 deaths a year. At 86.65 miles, I-12 is too short to rank against the 56 Interstates of 100 miles or more, so this page gives it no death rate.

St. Tammany Parish, at the Slidell end, had the most deaths with 36. East Baton Rouge followed with 28, then Tangipahoa with 18 and Livingston with 16. Deaths rose from 19 in 2021 to a high of 25 in 2022, dipped to 22 in 2023 and fell to 12 in 2024, a figure that still rests on NHTSA's preliminary 2024 data.

Counties with the most I-12 crash deaths

Bridges on I-12

I-12's main line rides on 107 bridges in the 2025 National Bridge Inventory, and not one of them rates Poor. Fair outnumbers Good, 63 to 44, and the median bridge was built in 1970, during the years the road was opening in sections.

The route crosses the Amite River near the East Baton Rouge and Livingston line, along with the Natalbany and Tchefuncte rivers farther east. Near Slidell, a $25.7 million project from January 2011 to summer 2012 widened I-12 to six lanes from the Vincent's Bayou Bridge east to I-10 and I-59.

Tolls on I-12

As of January 1, 2023, the FHWA toll inventory carried no I-12 entry. The Wikipedia and Interstate Guide pages on I-12 describe no tolled lanes opened after that date. Driving it end to end from Baton Rouge to Slidell costs nothing.

The nearest toll road is the Lake Pontchartrain Causeway, a separate bridge that reaches I-12 by way of US 190 near Mandeville and crosses the lake south toward Metairie.

How I-12 was planned, opened and widened

I-12 was added to the Interstate system on October 17, 1957, laid out from I-10 in Baton Rouge to I-59 north of Slidell. In the mid-1960s the plan changed so that I-12 and I-59 would both end at I-10 near Slidell. Wikipedia says the road opened in pieces from January 1967 to June 1976. Interstate Guide dates the first two miles, opened together with a piece of I-10, to 1965 and says traffic could reach US 51 Business at Hammond by 1972.

Hurricane Katrina damaged the I-10 Twin Span in 2005, and for a time I-12 carried the I-10 traffic between Baton Rouge and Slidell. The eastbound span reopened on October 14, 2005, and the westbound span on January 6, 2006.

In 1993 the Louisiana Legislature named I-12 the Republic of West Florida Parkway, after the short-lived republic that broke from Spain in 1810 and lasted 74 days. DOTD put up signs with the name and the republic's flag in 2003.

DOTD has been widening I-12 from four lanes to six in stages since the early 2010s. The stretch from O'Neal Lane to Walker was finished in April 2013. In St. Tammany Parish, a $54 million phase from US 190 to LA 59 started in May 2020 and a $59.1 million phase west from US 190 to LA 21 followed that fall. A third phase, LA 21 to LA 1077, cost $56.2 million and was finished by January 2026.

I-12 traffic and road conditions

All of I-12 is in Louisiana, so a single state 511 service covers the road from the Baton Rouge split to Slidell. Use the link below for current wrecks, lane closures and construction; the crash counts on this page end with 2024.

I-12 questions