NEW YORK — Poor domestic infrastructure investment and a general need for repairs have earned the United States’ public transportation infrastructure a D-plus grade from the American Society of Civil Engineers (ASCE) as steel industry leaders make insistent calls for a bigger investment in the nation’s infrastructure.

"Postponing action until more deterioration has occurred is not an acceptable approach," Steel Manufacturers Association president Thomas A. Danjczek told AMM. "U.S. policymakers need to take meaningful action to improve our economic well-being by rebuilding our decaying infrastructure and to ensure the recovery of U.S. manufacturing."

“The (ASCE) report is not surprising, given what we know about the state of our nation’s infrastructure," Thomas J. Gibson, president and chief executive officer of the American Iron and Steel Institute, said. "AISI has continually advocated for a robust increase in infrastructure spending to repair our nation’s crumbling roads and bridges, improve the economy and put Americans back to work."

The latest grade was a slight improvement over the D-minus the ASCE gave the nation’s infrastructure in 2009, reflecting an improvement in bridges, which received a C-plus; railways, which also received a C-plus; and roads, which received a D. But the report, which is released every four years, said the improvements had not gone far enough and increased infrastructure spending is necessary.

"While the modest progress is encouraging, it is clear that we have a significant backlog of overdue maintenance across our infrastructure systems, a pressing need for modernization, and an immense opportunity to create reliable, long-term funding sources to avoid wiping out our recent gains," ASCE said in the report, which called for $3.6 trillion in infrastructure investment by 2020.

The Infrastructure Jobs and Energy Independence Act, which was introduced in the House of Representatives last month, would provide funding for roads, bridges, locks and dams, as well as encourage growth in oil and natural gas. The AISI has endorsed the bill, calling it a boon for the steel industry.

Some sources were skeptical, however, that the government would be capable of mustering the funds.

"There are always bills and presidential announcements," Ken Simonson, chief economist for the Associated General Contractors of America, told AMM. "But the reality is that with the budget that the Senate is working on this week, I don’t see that increasing the door to federal funding."

Gasoline taxes—the traditional source of funding for infrastructure projects—are becoming insufficient to support U.S. spending, as higher gas mileage requirements and more gas-efficient vehicles reduce consumer fuel purchases and diminish the tax fund pool.

"Congress has been unwilling to address the gas tax issue," Danjczek said. "The debate over infrastructure investment largely centers on budgets and funding mechanisms."

Corinna Petry, Chicago, contributed to this story.