The Legislature approved a sweeping bill Thursday that would gradually boost state aid for roads and bridges by about $300 million per year, which would be the biggest investment in Louisiana's troubled transportation system in nearly four decades.

The House approved it 87-13 and the Senate did so 37-0 with less than an hour left in the session.

A key issue is whether Gov. John Bel Edwards will sign the measure, House Bill 514.

"I am not yet ready to tell you whether this bill will be signed," Edwards told reporters in his post-session press conference.

The hike would happen by gradually transferring 60% of sales tax revenue from the sale of cars and trucks from the state's general fund to one for transportation improvements only.

Backers said 75% of the money would be aimed at so-called mega projects, including construction of a new bridge across the Mississippi River in Baton Rouge, and 25% for preservation.

The vote followed days of behind-the-scenes meetings between Edwards and legislative leaders, including Wednesday evening and early Thursday morning.

House Speaker Pro Tem Tanner Magee, R-Houma, chief sponsor of the bill, implored House members to get behind the proposal.

Magee said he has watched the state make major investments in education, health care and other areas while road and bridge conditions routinely rank near the bottom in national surveys. "But the one thing we have never committed to investing is infrastructure," he said.

One of the key sticking points was whether lawmakers could craft a plan that Edwards could embrace without worries that it would drain the general fund of needed dollars for key state services.

The legislation includes provisions aimed at keeping that from happening.

The sales tax for the sale of cars and trucks generates about $500 million per year.

Under the bill, 30% of that revenue would be moved to a transportation fund in mid-2023 and another 30% the following year – 60% in all.

However, sponsors added a provision that would limit transfers to $150 million per year if state revenue projections forecast a drop of $100 million or more.

In addition, only $150 million of the new revenue could be tied up annually in borrowing costs, a move designed to stretch dollars but one that could also hinder efforts to shore up Louisiana's general fund.

Senate Transportation Committee Chairman Rick Ward III, R-Port Allen, Senate sponsor of the bill, said backers took deliberate steps to reduce chances than the transfers could worsen any future state budget crisis.

"We wanted to make sure we did this in a responsible way," Ward told the Senate.

The legislation, if signed by the governor, would be the biggest ongoing revenue boost for roads since the tax was boosted by eight cents per gallon, to 16, cents, in 1984, according to state records.

"The Legislature's action today is a major milestone toward reducing the state's backlog of infrastructure needs and positions Louisiana to compete economically with the rest of the nation," said Erich Ponti, director of the Louisiana Coalition To Fix Our Roads, a group of business interests that advocate for long-term funding for roads and bridges.

HB514 also represents a breakthrough for addressing transportation needs, which has sparked years of complaints by motorists in Baton Rouge and elsewhere about daily traffic backups without any permanent solutions from the Legislature.

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Efforts to boost the state gas tax, which is 20 cents per gallon, repeatedly fell on deaf ears in the House and Senate despite a $14 billion backlog of road and bridge needs.

Opponents have said their constituents are unwilling to pay more at the pump.

A short-lived push to extend the state's 0.045% sales tax, which is set to expire in 2025, to boost state aid for transportation by nearly $400 million per year was shelved earlier this week amid opposition from the House Conservative Caucus and others.

In 2019 the Legislature agreed to re-route more than $700 million the state is getting because of the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, which injected dollars into a handful of road and bridge projects.

But that aid was onetime compared to the transfer approved Thursday, which would raise about the same amount of money as a 10-cent-per-gallon hike in the state gas tax.

The bill was initially a simple measure to remove the state sales tax exemption from the sale of therapeutic marijuana.

However, once the measure passed the House efforts by Ward, Senate President Page Cortez, R-Lafayette, and others to rewrite the bill began, with an eye toward making a major impact on transportation.

The makeup of the negotiating committee that hammered out the final version of the bill pointed up its importance, including Cortez, Magee, Ward and House Speaker Clay Schexnayder, R-Gonzales.

The speaker said earlier that the 2021 regular session had the potential to include historic breakthroughs.

Cortez, Ward and Magee all played leading roles two years ago in the overhaul of the Deepwater Horizon money.

The money would target high-profile projects statewide, including the Baton Rouge bridge; upgrading U.S. Hwy. 90 between New Orleans and Lafayette to interstate standards and widening Interstate 12 roughly between Satsuma and the Mississippi line.

Scott Kirkpatrick, executive director of the Capitol Region Industry for Sustainable Infrastructure Solutions, said the bill would allow the Baton Rouge bridge to be built and be a "tremendous step forward."

Newly-added projects in the final version of the bill include widening Interstate 10 to eight lanes between Williams Boulevard and Veterans Boulevard in Kenner and I-10 from La. Hwy. 30 to La. Hwy. 22.

Sponsors of the bill insisted that this one is more likely to have an impact than a 2008 law that called for the transfer of $400 million in motor vehicles sales revenue from the general fund to the Transportation Trust Fund.

However, that law included a provision that said the transfer would only take place when state revenue reached a certain level, which never happened.

Email Will Sentell at wsentell@theadvocate.com.