The plan to widen Interstate 10 in Baton Rouge would not only add a lane in each direction.

It also would make huge changes to some of the exits along the 3.5-mile corridor between the Interstate 10/12 split and the Mississippi River bridge.

Gov. John Bel Edwards outlined his proposal last month, and state officials hope to start construction in 2019 or 2020 using federal bonds that the state would repay over 12 years.

Many details of the project are unclear.

"We can't speak with certainty because we are in the process," said Shawn Wilson, secretary for the state Department of Transportation and Development. "We can only tell you what the next phase is."

However, major changes are envisioned from the "new" bridge eastbound after nearly two decades of proposals, controversy and false starts.

Mississippi River bridge to Dalrymple

This section of the corridor is one of the biggest traffic chokepoints in the Baton Rouge area.

Motorists leaving the bridge and heading into Baton Rouge now have two eastbound lanes — briefly. The outside lane requires drivers leaving the bridge to quickly exit at little-used Washington Street.

That often sparks panic by motorists, who then force their way one lane over, and out of the Washington Street-bound lane, to continue eastbound on I-10.

Under the plan, what is now the Washington Street exit lane off the bridge would become the new eastbound lane that carries travelers through town to the I-10/12 split.

Motorists still would have the option of exiting farther east at a new, combined Washington Street/Dalrymple exit.

"That way, you will have two lanes coming from I-110 south and two lanes coming off the bridge," said Eric Kalivoda, deputy secretary for DOTD.

The current configuration narrows I-10 eastbound to three lanes after motorists leave the bridge.

In addition, the overhaul would add an eastbound I-10 path from Dalrymple, which has been discussed for years.

Motorists can currently use an on-ramp from Dalrymple to get to I-10 westbound. That would not change.

What is new is motorists on Dalrymple also would have the option to take a short frontage road toward Washington Street, cross under the interstate and loop around to a new, eastbound I-10 on-ramp.

"It would be a Texas turnaround," Kalivoda said. "Very similar to the one we have at Government Street, where you can turn around and go to the casino."

State Rep. Patricia Smith, D-Baton Rouge, who generally backs the governor's plan, said some concerns in the past about widening I-10 from residents in the Washington Street area have disappeared.

"The houses are occupied by renters because the majority of homeowners have died," Smith said.

Perkins Road overpass

Business owners in the area have long criticized I-10 widening plans and predicted that adding new lanes would destroy restaurants, bars and shops.

Kalivoda said the state may not need any right of way for that section of the widening.

The work can be done, he said, without putting more restaurants and bars literally under a revamped I-10.

The key? Closing the on- and off-ramps at Perkins, which would create space on both sides of the existing interstate.

"In removing those ramps, and of course we own the right of way that the ramps currently occupy, that gives us the room to widen and add additional through lanes," he said.

Most of the widening will be done on the outside of the roadway.

Lanes have to be 12 feet wide.

Acadian Thruway

At Acadian Thruway, the westbound on-ramp and the eastbound off-ramp would be lengthened.

Both would be done after the Perkins Road on- and off-ramps are removed.

The westbound on-ramp to I-10, which is near TJ Ribs, is especially troublesome, and some motorists avoid it.

"It is a very short on-ramp," Kalivoda said. "But we can't really lengthen it because the Perkins Road on-ramp is in the way."

The eastbound auxiliary lane between Acadian and College is expected to remain.

Some soundwalls in the area will be relocated on mostly state-owned property to allow for the widening.

College Drive

At College Drive, the widening means there will be four eastbound lanes crossing the College Drive overpass, and the College Drive on-ramp will make five.

Significantly, a new elevated express ramp will be added on I-10 for westbound drivers headed to College Drive.

The current pattern is this: Westbound motorists on I-10, after they pass Essen Lane, see that the interstate narrows from three lanes to two near the ramp for eastbound I-12.

That often results in motorists trying to wedge into traffic to avoid heading east on I-12.

The changes would eliminate the triple lane change that westbound I-10 drivers have to make to exit at College Drive.

No changes are planned for those headed to eastbound I-12 from westbound I-10, officials said.

What's next

Traffic through the entire corridor was built in the 1960s for around 80,000 vehicles per day.

Instead, more than twice that number use it daily.

According to projections, more than 200,000 vehicles will be using it daily by 2032, boosting travel times by up to 80 percent.

Wilson has said the work will take at least five years and more likely six or seven years, which means 2025 for completion or more likely 2026 or 2027.

The governor's proposal has cleared the House and Senate transportation committees.

It next faces action in the Joint Legislative Committee on the Budget, possibly this month, and then the State Bond Commission.

Baton Rouge-area lawmakers, Republicans and Democrats, generally support the governor's plan.

"It is the best opportunity we are going to have to get something done," said House Transportation Committee Chairman Kenny Havard, R-St. Francisville.

The I-10 work is the biggest part of a $600 million undertaking, including up to $110 million to finish an I-10 connection from Loyola Avenue in Kenner to Louis Armstrong New Orleans International Airport.

Also, work is about to begin on an earlier announced project in Baton Rouge to add a new exit off I-110 South. Southbound motorists on I-110 will be able to get off at Terrace Avenue and get to the Washington Street area without using the Washington Street exit, which would be used for eastbound cars and trucks leaving the bridge. The Terrace Avenue work is expected to take about 18 months.

The aim is to allow motorists on I-110 South to exit left rather than having to cross multiple lanes to exit right at Washington, which causes backups.

The larger interstate widening plan envisions the state repaying the bond money annually from a portion of annual federal highway aid.

Sen. Bodi White, R-Central, is among supporters of the effort.

"If we don't do that, we will never get to alleviate the traffic problem in Baton Rouge," White said.

Follow Will Sentell on Twitter, @WillSentell.