More than 70 transportation projects across Georgia could be delayed indefinitely because the federal Highway Trust Fund is running dry, state highway officials said.

In metro Atlanta, this might mean a redesigned interchange with additional left-turn lanes on I-285 at Flat Shoals Road in Decatur will have to wait. Another right-turn lane on the exit ramp of Ga. 400 North at Holcomb Bridge Road may be put on hold. Cars could keep stacking up in busy Buckhead because plans for a left-turn lane on Piedmont Road at Habersham Road could be pushed back.

And dozens of road resurfacing and bridge maintenance projects may be stalled, all because Congress has not acted to shore up the soon-to-be insolvent federal fund that pays for transportation projects across the country.

Federal dollars account for more than half the money in the Georgia Department of Transportation’s total budget. And about two-thirds of the money GDOT spends on capital improvements comes from the federal Highway Trust Fund.

But U.S. Transportation Secretary Anthony Foxx issued letter to state transportation department heads on Wednesday notifying them that the trust fund is projected to go into the red as early as August.

Without an infusion of cash from its general fund or a new surface transportation bill, the federal government won’t be able to honor its commitments to states for bridge, highway and transit projects.

Some states, such as Arkansas, have already been forced to shut down active construction projects because of the funding uncertainty.

GDOT Commissioner Keith Golden said Georgia won’t have to halt any active projects. But he has set a July 1 cutoff for authorizing new projects because of the uncertainty about how quickly Georgia would receive federal reimbursements.

About $200 million worth of projects that were set to begin this summer will be delayed indefinitely until the federal funding question is decided, he said.

“It’s a huge impact to our state,” Golden said. “Summer is usually our major construction season.”

The Highway Trust Fund receives the bulk of its revenue from the federal gas tax. The problem is, that tax has remained 18.4 cent per gallon since 1993. Meanwhile, Americans are driving more miles on less gas because of the proliferation of fuel-efficient vehicles.

The current U.S. surface transportation law, which dictates policy on how money is divvied up from federal gas tax revenue, expires Sept. 30. There have been hearings in Congress on a new bill, but no real movement.

A $302 billion Obama administration proposal relies in part on increased corporate tax revenue. Thus, it is unlikely to go far in the Republican-run U.S. House.

A short-term extension of current law is the most likely outcome this year, since far-reaching legislation is unlikely in an election year, said U.S. Sen. Johnny Isakson, a Georgia Republican.

He said Congress will have to dig in more next year on the issue, and there are a variety of proposals to address the transportation funding crisis.

One thing seems certain: The issue is starting to resonate with voters.

In a landline and cellphone survey of registered voters in Georgia conducted earlier this year by Purple Insights, 87 percent of respondents felt it was important that Congress take action to continue funding for transportation.

Almost three-fifths said they would be less favorable toward a member of Congress who was not working to continue federal transportation funding. The poll was commissioned by the American Road & Transportation Builders Association and the American Public Transportation Association.

Transportation advocates say federal transportation policy should be set in six-year increments, as opposed to short-term proposals, to provide enough certainty to plan for future projects.

But with the shaky outlook in Congress, the best solution might be finding a way for the state to become more self-reliant.

“It’s a precarious situation,” said Michael Sullivan, chairman of the Georgia Transportation Alliance. “We’re so reliant on federal funding, and it is so very uncertain as the hyperpartisanship becomes more and more severe. Georgia really has to look at how it can control its own transportation funding destiny.”

There are several options for doing that, though none are popular.

One idea is to raise the state gas tax. A hike of 6 or 7 cents per gallon would be needed to offset the declining federal revenue stream, GDOT’s Golden said.

Georgia currently levies two types of motor fuel taxes, an excise tax of 7.5 cents per gallon, plus a tax of 4 percent on the retail price of fuel.

Georgia could replace the state gas tax with a straight sales tax, as Virginia has done. Or, it could consider replacing the gas tax with a tax on the number of miles driven, an idea that was tested in Oregon. North Carolina has tried taxing gasoline as a percentage rather than a set amount.

Isakson said if such ideas prove successful, they can be taken to the national level to fix the trust fund.

“Transportation construction money has always been a partnership with the state, local and federal governments and it’s worked very well,” he said. “But you’ve got to have the capital to make the investment.”