The 2007 Minnesota bridge collapse led to concerns about US infrastructure
The state of America's infrastructure has not improved in the past four years, according to a report from the country's top civil engineers.
The "Report Card" from the American Society of Civil Engineers gives the US a D grade for its roads, public transport and other basic services.
It comes as President Barack Obama proposes to increase infrastructure spending to stimulate the economy.
An estimated $2.2trn (£1.5trn) is needed for repairs, the report says.
"In 2009, all signs point to an infrastructure that is poorly maintained, unable to meet current and future demands, and in some cases, unsafe," the report says.
"Since the last Report Card in 2005, the grades have not improved."
The ASCE graded America's infrastructure in 15 areas, including aviation, bridges, roads, rail, water, sewerage and energy.
The only area which saw any improvement in the four years since the previous report was energy, which the engineers graded as a D plus, up from a D in 2005, because of investment lined up over the next few years to "implement SmartGrid technology".
America's flood protection system, which the engineers had not previously graded, received a D minus.
"Much of the condition of the nation's estimated 100,000 miles of levees is unknown," the report said.
Mr Obama's $825bn stimulus package contains a number of infrastructure spending proposals, including $30bn for highway and bridge construction, $1bn for new commuter rail projects and $3bn for airport expansion.