Congress has been gridlocked on highway funding. Why that could be changing.

On Thursday, Congress yet again merely patched the nearly-depleted fund that pays for fixing America's highways – with the Senate passing a three-month fix and sending it to the president for his signature. 

It was the 34th patch since 2009.

But this time, the patch may pave the way to a longer-term solution. That solution is not in focus yet. But Congress's institutional body language was showing positive signs.

“I feel pretty optimistic,” said Sen. Barbara Boxer (D) of California at a press conference Thursday.

A worker in the trenches for years on this issue, she’s seen plenty of disappointment when it comes to funding infrastructure – not to mention her dismay at the recent collapse of a bridge on Interstate 10 that connects Los Angeles and Phoenix. Drivers have to go hundreds of miles out of their way.

But Senator Boxer’s smiling now. Momentum is building for Congress to pass a bill that funds America’s highway and transit system for six years. Thursday’s patch is meant to give both chambers time to work out that bigger plan.

They have a starting point. Just before passing the $8 billion short-term fix, senators passed a bipartisan, six-year highway bill with a strong 65-to-34 show of support.

It’s got some problems. The biggest is that it’s only funded for three of the six years. But it’s the first long-term highway bill to emerge from the Senate in a decade – the result of hard negotiating between Boxer and majority leader Mitch McConnell (R) of Kentucky, among others.

The House also has a starting point – though not in the form of legislation yet. Ways and Means Committee Chairman Paul Ryan (R) of Wisconsin would like to repatriate United States corporate earnings held offshore, bringing them back at a low tax rate. That money would help pay for highways for six years. It’s an idea that has general support from President Obama as well as Democrats in the Senate.

One potential compromise being discussed: Use the Senate bill funding for the first three years and fill the last three years with Representative Ryan’s tax reform.

But Republicans are talking about bringing this money back at tax rates that are substantially lower than what Mr. Obama has suggested. Senator McConnell is also skeptical of the plan, because he prefers broader tax reform under a potentially Republican president post-2016, among other concerns. Right-wingers, too, have their complaints.

That makes for a lot of roadblocks still to overcome.

Still, as the week wound down, key players expressed support for a House-Senate conference to work out a long-term bill. 

“We all want the House to have the space it needs to develop its own bill, because we all want to work out the best possible legislation ... in conference,”  McConnell said Thursday.

Outsiders, too, expressed hope. One reason is that lawmakers have chosen to avoid the highly divisive federal gas tax.

Upping that fee, which hasn’t been raised since 1993, appeals to lawmakers on both sides, but it’s also strongly resisted by both Obama and Republican leaders in Congress. 

An increase in the federal gas tax could be seen as a tax increase on the poor, because they don’t typically drive more-expensive, fuel-efficient cars. And given fuel efficiency, the power of the gas tax as a revenue raiser has weakened. Plus, some Republicans don't want to raise taxes, even for infrastructure.

“I’m optimistic they’ll find a longer term solution. There does seem to be bipartisan awareness and bipartisan support for funding this,” says Rick Geddes, a visiting scholar at the American Enterprise Institute think tank and an infrastructure expert at Cornell University in Ithaca, N.Y.

But even a six-year highway funding bill – which used to be the norm – is only an interim solution, Mr. Geddes says. “What’s going to come next?”

In his view, funding needs to move to an updated user-fee model, one that’s based on miles driven. Oregon is now moving toward full implementation of a mileage-based user fee and other states are studying it. High-speed, electronic toll collection is gaining traction, particularly on the East Coast. 

The Senate bill includes a provision to study mileage-based user fees.