Alaska’s bridge to nowhere is so seared in the minds of voters as the epitome of wasteful federal spending that experts say hardly anyone is willing to pay more to revitalize the nation’s aging highways, bridges and transit systems.

Despite dire warnings that a cancer is eating away the networks that carry people from place to place and goods to market, there is little urgency among the American people or political will in tight times on Capitol Hill to address the issue.

Faced with that grim assessment, an elite group of transportation experts that gathered in Washington last week did not pause to ponder the calamity they foresee if the public fails to grasp hold of the need.

They had done that a year earlier in a report that was a landmark for depth, scope and bipartisanship. More than 80 transportation experts joined in the conclusion that the federal government needed to spend upward of $60 billion more a year just to maintain the current systems and at least $85 billion more annually on expansion to accommodate a population that has more than doubled since the interstate highway system was begun 60 years ago.

Already sobered by the reality that, at the very best, Congress might vote to keep funding at current levels — roughly $54 billion a year — the career transportation experts received another dose of bad news last week.

Americans don’t trust their leaders — notably Congress — to spend transportation tax dollars wisely and are deaf to appeals for additional spending.

“The overwhelming sense that this thing has become a scam is very compelling,” said Jim Mulhall, a political strategist who has done focus groups for the advocacy organization Building America’s Future.

Led by five former secretaries of transportation — James Burnley, Samuel Skinner, Rodney Slater, Norman Mineta and Mary Peters — the group gathered at the University of Virginia’s Miller Center offices in Washington for two days of discussion on how to educate and energize average Americans about the catastrophe they foresee.

They were told that they had some hope of persuading those on the political left and center, but that “conservatives are utterly convinced that there is waste and corruption, and that no money [more] is needed,” said Rich Thau, of Presentation Testing, who has tested public opinion on the issue.

“They think somebody wasted my money and [that] it’s going to something else,” Thau said. “You can make a good case for infrastructure [improvements] but people still don’t want to pay.”

The infrastructure issue has played large within the Beltway, where think tanks, transportation advocates and some members of Congress wave around data that indicate that gridlock and economic stagnation will descend dramatically unless trillions of dollars are spent on roads, bridges, ports, transit and aviation systems.

But to much of the rest of the nation, transportation funding is synonymous with pork barrel spending and boondoggles.

Advocates have quantified the issue every which way in at least a half-dozen major reports and lots of smaller studies that singled out one slice of the transportation pie chart. Almost 70,000 bridges are structurally deficient, more than 20 percent of flights at the busiest major airports experience delays, the U.S. risks losing competitive ground on other nations that invest more, traffic congestion threatens to strangle the economic viability of big cities, long-neglected metro transit systems are breaking down, and the foundations are crumbling beneath that fresh coat of asphalt on millions of miles of highway.

None of that has persuasively connected with the public, the collected experts agreed.

“Ultimately, it comes down to a trust issue,” said Emil Frankel, an assistant secretary for transportation in the Bush administration who now works at the Bipartisan Policy Center.

Thau said that for years polling has shown many Americans believe about half of every dollar spent on transportation is wasted.

Congress has itself to blame for the deep public cynicism. Although earmarks became commonplace in bills of all sorts during the 1980s and 1990s, nowhere were the pet projects of individual members more likely to appear than in transportation bills. There were 6,000 of them in the last long-term transportation bill in 2005.

A $223 million bridge in Alaska proposed to replace a seven-minute ferry ride and serve an island populated by 50 people became notorious as the “bridge to nowhere.”

Though it was never built, that bridge became iconic as the ultimate self-indulgent pork barrel project, bandied about by presidential candidates and tea party nominees for Congress.

The transportation bills currently in play on Capitol Hill — one approved by a Senate committee and a House bill that has been described but not made public — are promised to be earmark-free.

But the damage of the bridge to nowhere and the legacy of earmarks cannot be surmounted unless those who advocate for an infusion of cash into infrastructure better communicate their urgency.

“People are much more open to additional spending if the impact on their local community is articulated,” said Catharine Ransom, whose Glover Park Group communications group was invited to the conference to help plan a strategy.

In addition to keeping the message local — referendums to spend on local transportation projects are approved overwhelmingly — advocates should focus on positive outcomes, like job growth, and emphasize the success of projects that come in on time and under budget. Warnings are rarely heeded, Ransom said.

“People are not receptive to messages that focus on negative consequences,” she said.