The gas tax that feeds the Highway Trust Fund is running out. Now what?

By Aug. 1, the Highway Trust Fund will not be able to pay all the bills for new projects, and with Congress nearing summer break, the days left to fix it are running short too.

The Congressional Budget Office says more than a quarter of highways and 65 percent of mass transit projects will see a drop in spending if something is not done.

At the White House, Vice President Joe Biden voiced his concern over getting the financing gaps filled, saying, "If Congress doesn’t act by September on the Highway Trust Fund, states are going to have to defer, delay or halt 112,000 active highway projects, 5,600 highway transit projects, putting at risk 700,000 jobs — and good-paying jobs."

The House Ways and Means Committee is working on a $10 billion stopgap funding plan for the Highway Trust Fund. To raise that money, the plan would use an approach called "pension smoothing," which allows employers to delay contributions to pension plans. That generates more tax dollars, since pension payments are tax-deductible.

The Senate Environment and Public Works Committee is proposing a six-year transportation plan. Sen. Barbara Boxer says the House of Representatives' short-term fix is not the answer. At a press conference on Capitol Hill, the California Democrat said, "When you look at the Highway Trust Fund, it's one of the most successful funds because it has a user fee and we have a user fee for it."

But few on Capitol Hill are willing to get behind a gas tax increase, though that's how the Highway Trust Fund gets its money in the first place. The tax has not been raised since 1993, and is not tied to inflation.

The fund's revenue has actually been dropping over this last generation because cars are more fuel-efficient and people are driving less.

President Barack Obama has put forward a $402 billion transportation bill that would add money to the fund by closing tax loopholes.

"No laws are broken [in my proposal]. We're just building roads and bridges like we've been doing for the last, I don't know, 50, 100 years," said Obama at an event last week in front of Washington, D.C.'s Key Bridge.

"But so far, House Republicans have refused to act on this idea. I haven't heard a good reason why they haven't acted. It's not like they've been busy with other stuff," he added.

But Obama's plan also makes no mention of the gas tax. Both parties are avoiding it, because any tax is a tough sell in this political environment. Even more so in this midterm election year.

What does it mean if the money runs out?

How likely is it for a gas tax reform to pass in Congress with all this political gridlock?

We’re already paying enough at the pump. How can you persuade the public to pay even more?

We consulted a panel of experts for the Inside Story.