By Kathleen Masterson
Light and strong, suspension bridges are ancient technology. But they are still the most economical and elegant way to cover a large distance. Take San Francisco's Golden Gate Bridge; it covers a bay nearly a mile wide.
The strength and versatility of the suspension bridge lies in its simplicity. It's just two cables strung across a rift, anchored on either side, holding up the roadway. This gives engineers the flexibility to build towers on land or water, depending on a site's geography.
Suspension bridges are an ancient but elegant technology. They're built to last, and some, like the iconic Brooklyn Bridge, are more than 100 years old. But none of them will last forever, so engineers are testing a system of sensors that will sound the alarm if a cable nears failure.
New York City's Brooklyn Bridge will light up at night this weekend in honor of its 125th birthday. The bridge was built stronger than necessary at the time, so it held up through the transfer from horse-drawn carriages to cars and trucks.
A towering new suspension bridge debuts in southern France. At its highest point, the Millau Viaduct is more than 1,000 feet above ground, and the French say it's the highest bridge in the world. NPR's Robert Siegel talks with Millau's mayor, Jacques Godfrain.
