The Millau Viaduct was designed by structural engineer Michel Virlogeux and British architect Norman Foster. It forms part of the A75 autoroute from Clermont-Ferrand to Pézenas and links two limestone plateaus: the Causse du Larzac and the Causse Rouge. It was formally opened on December 16, 2004, much to the applause of motorists and local residents.
Prior to the construction of the viaduct, the only way to cross the Tarn River was the bridge at the bottom of the valley. During heavy traffic periods, motorists would sometimes wait for hours in traffic congestion to make the crossing. The Effage group was contracted to construct the bridge, still operating today. Under the government agreement that the company holds, tolls can be collected for crossing the bridge for up to 75 years.
It took fourteen years of research and three years of construction for the Millau Viaduct project to become a reality. The geography and weather conditions in the region made it very difficult for the engineers involved. The finished viaduct is constructed of an eight-span steel roadway supported by seven concrete pylons. The pylons, including temporary ones, were assembled first. Once they were in place the roadway was slid across the pylon from both sides by hydraulic rams. Finally, masts were erected on top of the pylons and connected to the deck. When the connections were completed, the temporary pylons were removed.
Before the construction of the viaduct, no building site ever used such a mixture of technologies in one location. Lasers, GPS, sliders, self-climbing formwork, high performance concrete, and other advanced materials all made the final bridge possible. In total, the project used 127,000 cubic meters of concrete, 19,000 metric tons of steel, and 5,000 metric tons of pre-stressed steel for the cables. The construction of the bridge cost €394 million. The viaduct has been a complete success and has even become a tourist attraction in its own right. In 2008, 4,670,449 vehicles crossed the Millau Viaduct. The bridge will provide motorists to the area a spectacular view and a quick journey for the foreseeable future. The contractor claims that the bridge's lifespan will be at least 120 years.