And it's not only beautiful, it's also very useful. Before it was built, you had to go through small roads and villages, which, in addition to taking more time, was not very comfortable for the people living there.
The town is at the bottom of a very steep valley and it is very difficult to avoid (this involves extremely steep and narrow farm roads that are difficult to navigate without a small 4x4).
Has it prospered or faded now that there is no through-traffic?
The viaduct has made some villages on the plateaus much more accessible. Small industrial businesses have set up shop.
The only thing that sucks is that the little railway line will probably never reopen.
That’s quite the understatement. I remember taking one hour to get to the bottom of the valley from the Larzac, and then one hour again to get back up on the other side. We’d often stop for lunch or a coffee in Millau just to do anything at all that was not sitting in the car, but the city was entirely choked by this overwhelming traffic. The viaduct was a massive improvement. And sure, it affected local restaurants and bars, but the city is much more liveable now.
You thing during particular holidays the single lane somehow has even less lanes, less grade separation and such? That would be quite a phenomenon.
In particular most intersections on the now D809 are roundabouts, continuing on the D809 often requires making a turn on the roundabout, and roundabouts are notorious for gridlocking with high turn volumes. Let that gridlock cascade across multiple intersections and you now have rapidly deteriorating travel times.
At other times, traffic is less high so this gridlocking is less likely to occur.