Sen. Barbara Boxer gave a shout-out to American Trucking Associations last week, thanking the trade group for supporting higher diesel taxes dedicated to highway funding.

“They have been so forthcoming in saying we don’t mind paying a little more as long as it goes to highways,” Boxer told members of the Association of American Highway and Transportation Officials. “They are the only group that has come forward in that fashion.”

Boxer, who as chairman of the Senate Environment and Public Works Committee was one of the principal architects of the MAP-21 highway law Congress passed last year, asked the state officials to help with the most challenging transportation issue now on the congressional docket: ensuring solvency of the Highway Trust Fund.

“We’re at the moment of truth now. We have to find a source of funding,” she said.

She said that although the current fuel tax mechanism cannot keep up with the need for reinvestment in the long run, the concept of users paying for the roads must be preserved.

“Once we give up the idea of a fee-based system then we are in trouble.”

The current highway program expires at the end of September 2014, and the trust fund has just enough money to get through until then.

Sarah Puro, an analyst with the non-partisan Congressional Budget Office, said the CBO estimates that the fund can meet its obligations through fiscal year 2014.

For the current highway law, Congress had to add in extra money from a variety of sources, including an $18.8 billion transfer from the general fund, to make the program whole.

After September 2014, outlays will need to come down or receipts into the fund will need to go up, or a combination of both, Puro said.

Boxer and Rep. Bill Shuster, R-Pa., chairman of the House Transportation and Infrastructure Committee, already have begun high-level discussions on the bill.

“We are at a tipping point,” Shuster told the AASHTO members. “We need to figure out how to fund at necessary levels.”

Hill staffers at the meeting said they expect committee work on the bill to commence in the second half of this year.

Shuster said that part of his challenge is to educate the most conservative House Republicans on the need for federal participation in transportation.

Some House members hold that federal highway activities should be devolved to the states but Shuster believes otherwise.

“The Articles of Confederation didn’t work,” he said, referring to the first governing agreement among the 13 founding states of what became the United States.

One reason the Articles were replaced by the Constitution was that it became apparent that the country needed a stronger federal government to ensure regional transportation, Shuster said.

“The federal government has always and needs to continue to play a role in creating and maintaining the transportation system,” he said.

One of Shuster’s themes is a return to a more bipartisan approach within the Transportation and Infrastructure Committee. He said he is reaching out to the Democratic minority on the committee to strengthen relationships before starting negotiations on the bill.

He’s also stressing the need for public education on the importance of federal support for transportation.

“It’s lost on a lot of American people that it’s the national system that gets products to the store,” he said. “Educating people will be imperative to moving the surface transportation bill.”