The Millau Viaduct, the world's tallest bridge

Road Trip 2011: Filling the gap on the A75 autoroute from Paris to Perpignan, the Millau Viaduct rises up to 1,025 feet above the Tarn Valley below. And it looks good, too.

This is the Millau Viaduct, the tallest bridge in the world, which towers 1,025 feet over the Tarn Valley near Millau, France. Daniel Terdiman/CNET

MILLAU, France--You first see it from miles away. And after an afternoon spent driving toward it and weeks of planning a visit here, it's fair to wonder if it will live up to expectations. And there it is. And it's awesome.

This is the Millau Viaduct, the world's tallest bridge, which spans the Tarn River and the Tarn Valley here, in the central-south region of France. At 1,025 feet tall, and 8,071 feet long, it is a stunning architectural and design feat. And it is beautiful to look at as well.

Opened in 2004 to close the "missing link" on the A75 autoroute that connects Paris in the north to Perpignan in the south, the Millau Viaduct was the result of 17 years of ideas, proposals, and design that resulted in shaving 37 miles off the former route through the region. But rather than choose a mundane design that simply did the job, the French went big. Very big. And it works.

I got a chance to visit the Millau Viaduct as part of Road Trip 2011, and if you've followed these projects over the last six years and seen that I have a thing for bridges, you may have a sense of what getting to see the tallest one on Earth means to me. I'd heard about the Millau Viaduct for years, and when I began planning Road Trip for Europe, I knew I wanted to visit. Millau is not an especially convenient place to get to. Still, it had to happen.

First sketches
The bridge opened for traffic in late 2004, but that was 17 years after the project began. At first, in 1987, it was just sketches, and people didn't even know whether a new bridge here would be built to the west or to the east of town.

Efforts like this move slowly, and it was not until 1994 that the decision was made: the new bridge, formally linking Paris to Perpignan, would be built just a few kilometers east of Millau. Two years later, in 1996, the design for a cable-stayed bridge by Michel Virlogeux of the Ponts et Chaussees firm, which would be led by architect Norman Foster, was chosen as the winner from among a group of competing designs that included "a bridge of constant thickness, a variable thickness bridge, a viaduct with stays stretched under the deck, and a construction with one single arch," according to the bridge's official Web site.

And then, in late 2001, the first stone was laid, and the Millau Viaduct was one crucial step closer to reality.

Things moved quickly from that point forward. "By spring 2002, the first piers of the Millau Viaduct were rising skywards," the site reads. "At the same time, the anchorage points of the deck (the abutments) were appearing [below]. A few weeks were all it took to carry out the earthworks. Twelve months after the work began, the pier "P2" went higher than [328 feet]. A year later, on December 9, 2003, the concrete work was completed on time! And what's more, the record for the tallest pier in the world was set at" 804 feet.

The first work on the steel deck of the bridge commenced in the summer of 2002, and on March 25, 2003, the first deck section, which was 561 feet long, "was driven out into open space: this rolling out operation was a success. [Seventeen] others followed suit, at an average rate of one rolling out every four weeks." And on May 28, 2004, the joining of the north and south sections of the deck took place. On 28 May 2004, at exactly 2:12 p.m., the junction--or "clavage"--of the north and south sections of the deck took place 886 feet above the River Tarn.

This is the Audi RS5 that CNET reporter Daniel Terdiman is road-testing during Road Trip 2011, seen in front of the Millau Viaduct. Daniel Terdiman/CNET

The rest of the bridge's construction went swiftly. Just 24 hours after the junction of the two sections, the first installation of the towers began, followed quickly by the addition of 154 stays intended to support the bridge's deck. By the end of September 2004, the deck's surface was laid. And on December 16, 2004, the first traffic crossed the Millau Viaduct. All told, there had been six major pieces of work--the raising of the piers, the construction and "launching" of the deck, the joining of the two sides of the deck, the construction and installation of the towers, the addition of the cable-stays, and the laying down of the road surface.

The piers and cable-stays
While views of the Millau Viaduct tend to focus on the towers, and the cables--as well as the deck--the bridge wouldn't be possible without the seven piers that anchor it to the ground.

Below each pier, there are four "morocan" wells that go 49 feet below the ground, and which are 16 feet wide. At each pier foot, there is a foundation slab that is 9.8 to 15.4 feet thick. And while all seven piers meet the deck of the bridge at the same height, they each have their own individual height. From the north to the south, the seven piers have heights of 310 feet, 804 feet, 725 feet, 473 feet, 448 feet, 367 feet, and 254 feet.

For their part, the cable-stays--which came in 11 pairs per tower--are well worth noting. Each stay is comprised of between 45 and 91 steel cables, depending on their length, and each has seven strands of steel--"a central strand with six intertwined strands," according to the bridge's Web site. Each stay-cable strand "has triple protection against corrosion: galvanization, a coating of petroleum wax, and an extruded polyethylene sheath. The exterior envelope of the stay-cables is itself equipped along the entire length with a double helical weather-strip," the site reads. "This is to prevent water running down, which, in the event of high winds would cause the stay-cables to vibrate, which in turn would affect the stability of the viaduct. The stays were installed using a well-tried technique. After threading one strand in the outer protective sheath, it is pulled up on to the pylon to its final location. The strand is then fixed in the upper and lower anchorage points. A 'shuttle' then brings the other strands one by one, and they are then stretched to tension."

All told, the stay-cables weight about 1,500 tons. There are also 36,000 tons of steel in the deck of the bridge.

A towering achievement
I live extremely close to one of the world's greatest bridges--the Golden Gate Bridge--and have spent a lot of my life admiring others all over the world from up close. I'd like to say I'm hard to impress when it comes to bridges, but that's actually not true. All it takes is a great setting and a little aesthetic appeal. That's why even the smallest one in Amsterdam, or the biggest one in New York City can fill me with equal enthusiasm.

After hearing for years about the world's tallest bridge, I wondered what it would be like, even though I'd seen pictures. And all I can say, now that I've visited Millau and looked at the viaduct from seemingly dozens of different angles, is that the people behind the project earned their money. They could easily have botched the job and made something that ruined the view of the lovely Tarn Valley. But in choosing a cable-stay bridge, making seven towers, and using the white color that they did, it's easy for me to give a big thumbs-up.

Would I recommend a visit? The truth is, Millau is not likely to be convenient on many tourists' itineraries, but if you're in the region, I would definitely say take a detour and check it out. And now that the bridge is there, if you happen to be driving from Paris to Perpignan, it's right on your way.

 

Join the discussion

Conversation powered by Livefyre

Don't Miss
Hot Products
Trending on CNET

TechProbe Volunteers Wanted: Huawei Mate 7

Your chance to test drive and keep the Huawei Mate 7 phone

Tell us about the technology you're using right now, and how a smartphone could help you in your professional life.