I live not too far away from the A3 Hindhead tunnel in Surrey. It opened in 2011 and was one of the few recent major road projects in Britain that managed to unite both the road-building and environmental lobbies. The last remaining single carriageway section of the London-Portsmouth A3 trunk road had been a notorious bottleneck for years. It ran around the Devil’s Punchbowl, the head of a steep valley in Hindhead, and the road could not have been easily widened even if that had been desirable. It wasn’t, because it ran between two large areas of heathland owned by the National Trust. Instead, the construction of the tunnel meant that the old A3 was closed and grassed over, allowing the reunification of the two pieces of National Trust land. The result was a much larger piece of heathland, benefitting wildlife and visitors alike, and relieving the residents of Hindhead of heavy through traffic, congestion and air pollution.

Before the tunnel’s construction, there was considerable debate about how the Hindhead bottleneck should be relieved. Early proposals (the Red Route) in the 1980s suggested a bridge across the valley. That had been rejected as quite unsuitable. After all, how could you put a big new bridge into an area of natural beauty without ruining the very area you were trying to save from the old road? I must admit that I was one of those who thought the whole idea of a bridge was complete nonsense.

However, the example of Millau in France suggests that rather than being nonsense, it might have been an idea ahead of its time. By 2004, and the public inquiry into the Hindhead bypass, the debate had moved on to examining the tunnel proposal and possible alternatives on the same alignment. There was a somewhat fringe pressure group (without which no British transport-related public inquiry is complete) which wanted the new tunnel and the retention of the old A3, completely negating the environmental advantages of the tunnel. Yet in the same year, 2004, similar traffic problems in Millau were brilliantly solved through the opening of a new bridge, long after such a solution had been rejected for Hindhead.

Nestled in the steep-sided Tarn Valley in southern France, in the 1990s the town of Millau faced a similar problem to Hindhead. It sat on a missing link of the A75 from Paris to Béziers. Filling in that missing link would allow traffic to be redirected away from the town, speeding up traffic that had no interest in being in Millau anyway, and making the lives of Millau residents much more pleasant.

The only problem was the deep and steep sided valley itself. North and south of Millau, the A75 ran at the level of the hills either side of the valley and there was no easy way of crossing it. Three horizontal alignments were considered, but even when those had been narrowed down to one preferred route, there was still the question of the vertical. The new road was either going to have to go right across the top of the valley, or down to the bottom and across the river Tarn, or some combination of both. After much consideration, the French government decided in 1991 that going straight across the top – a distance of 2.46km – was the preferred choice on the basis it would lead to faster journey times and cause less disruption to Millau.

An absolutely enormous viaduct would be needed. Not only would it be 2.46km long, but the bridge deck would be something like 200m above the ground over the deepest part of the valley. It sounded barely believable, but because this is France, where grand projets are something they cook up over coffee and croissant and deliver by the time they’re ready for mussels and chips in the evening, they got to work.

The Millau Viaduct actually took a little bit longer than that. Engineering studies needed to be carried out, and a final concept for the bridge selected. British architects Foster+Partners worked with structural engineers to produce a cable-stayed bridge design. Then, after further refinement of the detailed design, there was the competition to select the consortium to build it. It was 1999/2000 before Compagnie Eiffage du Viaduc de Millau, which again included Foster+Partners, was chosen. But thanks to all the preparation work that had been done in advance, it took just four years to build what remains the world’s tallest bridge (although subsequent bridges have been built with decks which are further above ground level).

The road deck is carried on seven enormous pylons, and cable stays are used to support the deck from them. The tallest pylon is 343m in height, considerably taller than the 300m Eiffel Tower, another tall building in France that quite a few people might be aware of. To allow for thermal expansion and contraction of the bridge deck, the pylons of the Millau Viaduct split under the road deck, an arrangement mirrored above by A-frame structures which hold the cables. Unlike many cable-stayed bridges where there are twin masts on the outer edges of the road deck, the Millau Viaduct has single masts between the northbound and southbound carriageways. It’s a fantastically elegant solution, the sort of thing you only get by having an architect involved early in the process. The arrangement allows for uninterrupted views along the valley from the bridge deck, the only downside of which is that some drivers slow down to admire it. There’s a windbreak along the edge of the bridge deck, a necessity given the windy conditions on a tall bridge, and this also prevents drivers from a having a view straight down, which I imagine might lead many drivers not just to slow down, but instead to execute a sharp u-turn out of sheer terror.

The bridge deck itself was a significant technical challenge. It took several years to identify a road surface mixture that would give the required durability, yet be flexible enough to cope with the bridge deck’s movements due to wind and temperature changes.

Viewed from a little further along the Tarn valley, it’s hard to avoid anthropomorphising the pylons, though they actually look more like seven giant robots, impassively supporting the road deck in their arms and studiously aloof; ignoring one another as they stand guard over Millau. There is nothing on their scale anywhere close to them to distract from their presence.

This huge structure really ought to ruin its beautiful environment, and indeed there were many environmental concerns expressed about the bridge during its development and construction phases. It doesn’t though, because the Millau Viaduct is a thing of immense beauty itself. It reaches for the skies and in turn elevates the souls of the those looking at it and driving across it. It evokes a similar feeling to the slender columns and pointed arches of the great Gothic cathedrals of France, that somehow this is a structure not entirely of earthly day-to-day concerns, but of some greater process. Sometimes the bridge deck sits above clouds which form in the valley below, reinforcing its lofty concerns, not to mention demonstrating why the solution of crossing the valley at the top was a better technical solution than going down to river level. Meanwhile, the repeating rhythm of the cable stays verges on the sculptural, lending a Barbara Hepworth-like sensibility to the viaduct.

It has been taken to heart by locals and visitors alike. Of course it has. Like any dramatic and well-designed intervention in the landscape, everybody hates it at first and then decides they liked it all along. There are two separate visitor centres connected with the Millau Viaduct, and it is an enormously popular photographic subject. It has become a much-loved local landmark. It also hosts a running race every other year, during which the bridge is closed to traffic.

The Millau Viaduct shows that a well-designed piece of transport infrastructure can not only avoid ruining an area of great natural beauty, but can actually be an enhancement to it. That should give pause for thought to those who wanted to bury Britain’s proposed High Speed 2 railway in a tunnel as it crosses the Chilterns (but it won’t). Visual intrusion is not about the presence of transport infrastructure, it’s about the quality of design. Badly designed pieces of infrastructure will always ruin their surroundings, but good ones can make a positive contribution.

Even today, as I walk around Hindhead, I sometimes wonder what a bridge would look like there. While I used to think the Devil’s Punchbowl had had a narrow escape, now I sometimes think the Red Route might have been something special, after all.

Bibliography and Further Reading

Foster+Partners’ project page for the Millau Viaduct, here

The official website of the Millau Viaduct, here. Reproduction of photos of the Millau Viaduct is quite strictly controlled, but permissible as private use on a personal blog; see note 1 on this webpage.

How to find the Millau Viaduct

Click here for The Beauty of Transport‘s map