The Millau Viaduct (12) on the A 75 motorway will be among the most striking civil engineering structures to be built at the start of this century.
The highest point of the multi-stayed viaduct is at 340 metres.
It is a unique structure, 2,5 km long, which will cross the Tarn Valley and forms part of the A 75 motorway which will link Clermont-Ferrand to Béziers and Montpellier (via the A 750 spur).

But, before we get to this point ........

1988 : ROUTES CONSIDERED,REASONS FOR THE CHOICE

The 4 route options examined in 1988 :

The "Eastern" option (yellow route), passing east of Millau with a high-level crossing of both the Tarn and the Dourbie valleys via 2 major bridges
(spans 800 to 1000 m).
These would have presented structural problems caused by siting the piers on a slope.
This option allows access to Millau only from the Larzac plateau, via the long road winding down from La Cavalerie.
Although shorter and better for through traffic, this route was rejected because it did not provide satisfactory access to Millau and the surrounding areas.

The option "following the RN 9 line "(red route) : providing good access to the town of Millau but presenting serious technical problems (tunnels, viaducts, major earthworks). This option was rejected because, in addition to thetechnical problems, there was a highly unfavourable impact on existing and planned urban development.

The "Western" option (blue route) :
about 12 km longer than the preceding option, it followed the Cernon valley and bypassed the north-west section of the Causse. Although technically easier and providing good access to theSaint-Affrique area, this option would have adversely affected the environment of two very attractive villages - Peyre and St. Georges de Luzençon. It was also more expensive (longer, with four viaducts) and with poor access to Millau. It was thereford rejected.

The "Median" option (light blue route) : had widespread local support but a priori presented major geological problems, particularly with regard to the crossing of the Tarn valley.Studies by experts led to the conclusion that there was a feasible solution which overcame some of the geological problems.
This "Median" option also proved 300 millions FF less expensive than the "Western" option. It received virtually unanimous support from local authorities.

Choice of a "Median" solution :

The "Median" option was approved by ministerial decree on 28 th June 1989. However, the decree stipulated that further in depth studies should be carried out : on the line of the route, the longitudinal profile and the type of structure to be used. Two new groups of alternatives were therefore considered.

The "high level" group integrating a 2 500 m viaduct and crossing the Tarn at a height of over 200 m.

The "low level" group : which comes lower down into the valley, crosses the Tarn on a 600 m structure and then reaches the Larzac using a 2 300 m long viaduct extended by a tunnel.

The high-level and low-level solutions were extensively analysed in the Aix en Provence Centre for Technical Design Studies (CETE)'s draft design plans before a solution emerged.
The high level group proved to be the better option, being technically less complex (in particular, there was no need for a tunnel), shorter, costing less overall, providing enhanced safety for road-users and having less impact on urban development. It also attracted widespread local support. And so the chosen option went to public enquiry at the end of 1993.

After being accepted by the public enquiry and the Council of State, it was declared to be in the public interest on 10th january 1995.

Top of page

The Routes

Under-braced viaduct



Viaduct with central



Viaduct of constant thickness



Viaduct of variable thickness



Multi-stayed Viaduct
The Chosen Solution

• 28 June 1989

• 29 October 1991

• July 12 1993

• November 1993

• 2November 1994

• January 10 1995

• April 1996

• 8 and 9 July 1996

• December 14 2001

Special procedures for a special structure. Once the route had been decided, after years of investigations and debates, five teams of design engineers and architects, each working on a group of solutions, were invited to submit their proposals on 23 April 1996.
The department of Transport followed the advice of the international jury and selected the "multi-stayed" option from SOGELERG-FOSTER.

This is a structure 2460 m long, consisting of eight cable-stayed bays, the longest of which is 342 m. The 2-lane dual carriageway suspensed almost 270 m above the Tarn will follow a wide curve with a slight gradient of 3 % to improve visibility on the structure and protect road-users.

Lateral screening is designed to reduce wind effects. The seven bridge piers will be built of reinforced concrete, in the form of pyramids splitting into reversed V-shapes ; thereby providing anchorages for the splayed cables.

The tallest pier unit will reach a height of 340 m, as tall as the Eiffel Tower.

About 127 000 m3 of concrete, 19 000 tons of reinforcing steel and 5 000 tons of prestressed steel ( cables and stays) will be needed to build the structure.

LE VIADUC DE MILLAU : UN OUVRAGE CONCEDE.

Four Years Work :

The state designated EIFFAGE as Prime Contractor.

Operational site management is the responsibility of the Interdepartmental Division of Civil Engineering Structures (A.I.O.A) under the management of Georges Gillet and attached to the Aveyron D.D.E. They will manage the construction of all structures over the 340 kms of the A 75.

Works on the Millau viaduct are expected to last four years. It is estimated that 400 people will be permanently employed on the construction of the viaduct.

Date of opening to traffic : 16 December 2004.

MILLAU VIADUCT :
BRIDGING THE RIVER TARN
The Causse Rouge is west of Millau. It will be the northern access to the viaduct. Once theTarn has been crossed, you are on the Causse du Larzac