Is America's future prosperity crumbling?
OHIO/TENNESSEE/GEORGIA -- Every working day, once in the morning, and again in the evening, Sarah Blazak drives at snail's pace in heavy traffic across one of the most dangerous bridges in America.
It's the Brent Spence bridge, and it spans the Ohio river, linking the state of Ohio to the north with Kentucky to the south. And according to US safety officials, less than 50 years after it was built, it is now "functionally obsolete".
It carries more than twice as much traffic as it was designed for, it has no emergency lanes for vehicles that have broken down, and its traffic lanes are too narrow.
Accidents are frequent - I saw a car that had smashed into the side of the bridge when I drove across just a few days ago, causing chaos as police struggled to remove it - and there have been at least two fatalities in the past two years.
"Every day when I get across, I breathe a sigh of relief," Sarah told me. "I'm closer to where I need to be, and I'm safer."
The Brent Spence bridge is just one example of a problem that is of increasing concern to the US - its crumbling infrastructure. Roads, bridges, ports and airports -- many are in desperate need of repair or replacement - and the resulting delays are costing the nation billions of dollars a year.
(The Brent Spence bridge is estimated to cost an annual 80-90 million dollars in traffic delays - because the I-75 interstate highway that it carries is one of the country's main north-south arteries. More than $400 billion worth of freight crosses the bridge every year.)
So why don't they build a new bridge? Simple answer: because they can't agree on who should pay for it. The present one was built mainly with funds from the Federal government in Washington - but there's no cash available from that source any more, and neither Kentucky nor Ohio much like the idea of picking up the tab themselves.
None of this would matter very much to people outside the immediate region, perhaps, if it wasn't a typical example of a much wider problem. The US has long been the world's dominant economy, a global leader in manufacturing and technological innovation - but the question is for how much longer?
Consider this: each year, the US turns out something like 100,000 newly qualified engineers. They're the ones who build the roads and the bridges. India and China, on the other hand, each produce a million new engineers, which means they have a lot more people available to build that all-important infrastructure without which no developed economy can prosper.
If you want to take a gloomy view of America's economic future, you could point to its continuing sluggish economy, an education system that isn't producing anything like enough mathematicians and scientists, and a corporate environment in which cash for research and development may soon start drying up as CEOs worry whether steady growth will ever return.
On the other hand, if you come to Atlanta, Georgia, where I spent the day yesterday, you'll find plenty of people at the Georgia Institute of Technology who are full of hope for the future. Lots of new ideas are bubbling away, they say - new materials to replace steel, new ways of producing cleaner energy, even new ways to produce robots with a sense of music - and yes, there's still money to fund the research.
Next Tuesday, we'll be broadcasting a special programme to explore some of these themes, with the help of a panel of experts at the Council on Foreign Relations in Washington DC. It'll include my report from the Brent Spence bridge, and later in the week, we hope to broadcast my report from Georgia Tech.
Meanwhile, if you're on Facebook, do take a look at The World Tonight Facebook page, where you can see some wonderful photos from our travels in Illinois, Ohio, Tennessee and Georgia, taken by producer and ace photographer Dan Isaacs.