A $675 million per year state sales tax hike for roads and bridges cleared its second hurdle Tuesday when the Louisiana House Appropriations Committee approved the measure.

The proposal, House Bill 778, next faces a showdown vote in the full House, with a daunting two-thirds approval needed for passage.

However, the approval of a major tax increase for transportation by one of the Legislature’s key panels marks a dramatic turnaround from recent years when similar bills were doomed or not even offered.

The legislation would boost the state sales tax by 1 cent.

That means purchases in East Baton Rouge Parish would include a total 10 percent charge for state and local taxes.

The money raised would finance a wide range of major projects statewide, including construction of a new bridge over the Mississippi River in Baton Rouge that connects La. 1 and La. 30; improvements to the Port of New Orleans; and upgrades to Interstate 49 between Lafayette and Broussard.

Backers said the measure is the only way that the state will see any major highway and bridge improvements.

“We are working on the whole picture,” said House Transportation Committee Chairwoman Karen St. Germain, D-Pierre Part and sponsor of the bill. “This is just one piece of the puzzle.”

The lawmaker is the sponsor of separate legislation — House Bill 777 — that would boost Louisiana’s gasoline tax by 10 cents per gallon.

That would raise about $300 million per year, or nearly $1 billion annually if both bills win final approval.

The gasoline tax increase is awaiting action on the House floor and it too needs a two-thirds majority for passage — 70 votes in the state House.

The session ends on June 11.

The sales tax bill is the latest, and most ambitious, effort to raise more dollars for roads and bridges. The state faces a $12 billion backlog of transportation needs. However, bids in recent years to tackle the issue have gone nowhere.

Rep. Patrick Connick, R-Marrero, a member of the committee, questioned how voters can be assured that the dollars will be used as advertised and whether the sales tax hike is enough to fund the 16 projects listed in the bill.

“We don’t want to see the money wasted,” Connick told St. Germain. “You just need to make sure this bill is rock solid.”

Backers noted that, under the bill, revenue raised by the sales tax boost would be placed in the newly created Major Economic Development Corridors Fund.

That would be separate from the Transportation Trust Fund, which is part of the state Department of Transportation and Development and a key source of road and bridge funding.

Supporters said cost estimates include 10 percent for inflation.

That issue — higher than expected costs — has plagued another road and bridge building program that voters approved in 1989 called TIMED.

The bill earlier won approval in the House Ways and Means Committee.

Backers on Tuesday included the Baton Rouge Area Chamber and GNO Inc.

The push to aid roads and bridges comes amid a state budget shortfall of $1.6 billion to keep spending at current levels.

Motorists pay 38.4 cents per gallon in state and federal taxes.

Follow Will Sentell on Twitter, @WillSentell. For more coverage of Louisiana government and politics, follow our Politics blog at http://blogs.theadvocate.com/politicsblog.