WASHINGTON - The collapse of two bridges in the United States in recent days has reignited a fierce debate about America's crumbling infrastructure while shining a startling spotlight on the state of the country's aging highways, bridges and overpasses.

Seven people were injured Saturday in southeastern Missouri after two freight trains collided and took out a nearby overpass. There were no vehicles on the overpass as it collapsed, but two cars crashed as they approached the bridge after it had crumpled.

The collision came just two days after a span of a heavily travelled interstate bridge over the Skagit River in Washington state collapsed.

That incident had a Canadian angle — the trucker, Alberta's Bill Scott, was hauling an oversized load that clipped an overhead girder, causing the bridge's collapse. Scott's Canadian employer, Mullen Trucking, says it received a state-issued permit to carry the oversized load across the bridge, located about 130 kilometres south of the Canadian border.

U.S. regulators have called the steel bridge, built in 1955, a "fracture critical" structure, meaning it could collapse if a single, critical component is compromised.

The bridge has a sufficiency rating of 57.4 out of 100, well below the statewide average of 80 — but 759 bridges in Washington state have a lower score.

The Skagit River bridge is among thousands across the country that share the same "fracture critical" designation, even if they've been deemed structurally sound.

In March, an organization of civil engineers gave the U.S. a D+ grade in infrastructure, and warned that one in nine bridges is structurally deficient — and more than 200 million vehicles cross those bridges annually.

Not surprisingly, the most recent bridge collapses have renewed long-standing calls for Congress to start spending money to repair the nation's crumbling infrastructure. Spending on public construction in the U.S. has dropped to its lowest point in 20 years in the aftermath of the 2008 economic downturn.

State and local governments, strapped for cash, have been cutting spending on infrastructure over the past five years. Spending on transportation in California, to name just one example, plunged by 31 per cent from 2007 to 2009.

Congress, meantime, hasn't stepped in to help.

In President Barack Obama's original economic stimulus bill of 2009, $48 billion was devoted to transportation spending — but that wasn't enough to make up for the drop in funding at the state and local levels. The most recent congressional highway bill, meantime, kept federal funding at current levels rather than boosting them.

One Washington state Democrat blames congressional Republicans for the current state of affairs, and what he describes as their steadfast determination to block Obama's legislative agenda at every turn.

"They have clearly spent the whole last five years trying to tear the president down, but they have done it by throwing the American infrastructure and the society under the bus," congressman Jim McDermott said recently.

"We have the most long-term unemployed that we have had since the 1930s and there's no excuse for that. There is plenty of work in this society that needs to be done and all it means is that the Congress has to step up, put the money up, and we can have it."

Sen. Frank Lautenberg, a New Jersey Democrat, is calling on Congress to pass a bill that would establish a new $5 billion fund for infrastructure projects in the aftermath of the Washington bridge collapse.

"Far too many bridges across the country and in my home state of New Jersey are aging and in urgent need of repair," he said.

The American Society of Civil Engineers says there needs to be an annual infrastructure investment of $20 billion over the next decade, a 60 per cent increase in spending. The Federal Highway Administration is calling for the same cash infusion.

In his latest budget proposal released last month, Obama reiterated his call for US$50 billion in infrastructure spending, pointing to the need to repair the 70,000 bridges across the country found to be "structurally deficient."

He also proposed, once again, a federal infrastructure bank that would give grants and loans to private companies to beef up transportation systems.

As always in the U.S. capital, the devil is in the details. While some Republicans support boosting infrastructure spending, the parties are brawling about how to pay for it.

The White House wants to use money freed up by ending the wars in Iraq and Afghanistan, but Republicans say those are false savings and add the proposal would further fatten up the mammoth national deficit.

"All of the infrastructure projects I know are based upon running up more debt, which is a very bad idea," Lamar Alexander, a Republican senator from Tennessee, told the Wall Street Journal.

The U.S. Chamber of Commerce has been pushing lawmakers to hike the 18.4-cent federal tax on a gallon of gasoline, which has remained unchanged since 1993, in order to fund infrastructure spending. Few legislators have the stomach to propose new taxes, however.

McDermott isn't one of them.

"We haven't raised the gas tax for bridges and highway since 1993," McDermott said. "And there is just no reason that we shouldn't be doing this and putting America back to work. All the other problems that face us would be gone if we had put people back to work."

The chairman of the National Transportation Safety Board, meantime, says the Washington bridge collapse, in particular, is a wake-up call for the nation.

"This is a really significant event and we need to learn from it, not just in Washington but around the country," Debbie Hersman said in Seattle over the weekend after taking a boat ride on the Skagit River below the bridge.

"At the end of the day it's about preventing an accident like this."

Canada, too, is facing calls for increased infrastructure spending. A study by the Canada West Foundation, released in February, warned that aging infrastructure threatens the country's economic growth.

Canadian cities and towns are urging Ottawa to double its annual budget for infrastructure to $5.75 billion, as well as commit to long-term funding so they can tackle decaying roads, bridges and water systems.

News from © The Canadian Press, 2013