The Millau Viaduct Over the Rivier Tarn

The lowdown on the tallest vehicular bridge in the world which spans the valley of the Tarn River. Interesting facts as well as information to make the most of your visit...

The Millau Viaduct (Viaduc de Millau) is a cable-stayed, masted bridge that spans the valley of the River Tarn near Millau, in the département of Aveyron. The bridge spans the 2.46 Km between the Causse du Larzac and the Causse Rouge.

Designed by French bridge engineer Michel Virlogeux, Dutch structural engineering firm ARCADIS and the English architectural firm Foster + Partners, it is the tallest vehicular bridge in the world.

Purpose

Part of the A75-A71 autoroute south from Paris to Béziers, it was constructed to divert heavy traffic off of the N9 through Millau. Before the viaduct was built, traffic had to descend into the Tarn River Valley to cross the river, causing congestion near Millau.

Though the bridge has the distinct purpose to move people across the Tarn River Valley, it was constructed to have as little visual interruption on the valley as possible. It is often described as "transparent" due to its delicate aesthetic nature.

Dimensions

  • The two outside spans are 204m long, while the six interior spans of the bridge are each 342m long
  • Its seven concrete pylons/masts are from 75 to 245m in height (taller than the Eiffel Tower)
  • The masts rise 90m above the deck, and each pylon/mast splits, forming a shape similar to the eye of a needle, in order to reduce the visual impact of the bridge
  • The deck is 32m wide, with two lanes and a safety lane in either direction
  • The deck is 4.2m deep. In order to give drivers better visibility, it curves in a plane section with a 20 Km radius. It has an ascending slope of three percent from north to south

Construction

Construction began on 16 October 2001 with the erection of the support pylons. Each pylon is supported by four shafts which are each 15m deep and 5m in diameter.

After the pylons were erected, each half of the deck was constructed and pushed across the valley using satellite-guiding to meet in the middle. This method required a complicated system of hydraulic cylinders and wedges to move the deck horizontally across the chasm. Temporary columns supported the deck as it slowly moved (600mm every four minutes) across the valley.

  • For a simplified diagram of this system from the BBC News: Click here
  • Or, for an in-depth animation of the process, with French commentary, see the official Millau Viaduct website: Click here

On top of each pylon is a mast, to which the cables (stays) supporting the deck are attached. The stays are made of 55 to 91 steel cables, each formed by a central strand with six intertwined strands. Every strand is galvanised, coated in wax and sealed in a thermo-plastic covering. The outside of each stay is weather-proofed. It is vitally important to protect against standing water and water penetration which could cause vibration in the stays during high winds and make the viaduct unstable.

The viaduct is rigged with a multitude of sensors and communication devices which constantly record and analyse, among other things: movement, traffic, weather and wear on the structure.

It took 14 years of research and three years of construction to create the Millau Viaduct. It was formally dedicated on 14 December 2004 and opened to traffic on 16 December 2004.

Cost

The Eiffage Group paid the €400 million construction costs in exchange for a concession to collect the tolls until 2080. If the bridge proves particularly profitable, the government of France has the option of taking over the bridge from Eiffage in 2044.

Interesting Facts

  • Although the Millau Viaduct is the tallest vehicular bridge in the world, the Royal Gorge Bridge in Cañon City, Colorado (USA) is still the highest suspension bridge in the world
  • The viaduct has the tallest pylon in the world, with pylon 2 standing 244.96m in height
  • It took ten years of research to develop the optimum formula for the deck surface material
  • The Millau Viaduct weighs 290,000 tonnes

Further Information