Let's go back and look at the history of Arenberg in Paris-Roubaix:
Introduced in 1968, the passage was closed from 1974 to 1983 by the Office National des Fôrets. Until 1998 the entry to the Arenberg pavé was slightly downhill, leading to a sprint for best position. The route was reversed in 1999 to reduce the speed. This was as a result of Johan Museeuw's crash in 1998 as World Cup leader, which resulted in gangrene so severe that amputation of his leg was considered.
In 2005 the Trouée d'Arenberg was left out, organisers saying conditions had deteriorated beyond safety limits as abandoned mines had caused sections to subside.
The regional and local councils spent €250,000 on adding 50 cm to restore the original width of three metres and the race continued using it. The Italian rider Filippo Pozzato said after trying the road after its repairs:
It's the true definition of hell. It's very dangerous, especially in the first kilometre when we enter it at more than 60kh. It's unbelievable. The bike goes in all directions. It will be a real spectacle but I don't know if it's really necessary to impose it on us.
In 2001 a French rider, Philippe Gaumont, broke his femur after falling at the start of the Trouée when leading the peloton. He said:
What I went through, only I will ever know. My knee cap completely turned to the right, a ball of blood forming on my leg and the bone that broke, without being able to move my body. And the pain, a pain that I wouldn't wish on anyone. The surgeon placed a big support [un gros matériel] in my leg, because the bone had moved so much. Breaking a femur is always serious in itself but an open break in an athlete of high level going flat out, that tears the muscles. At 180 beats [a minute of the heart], there was a colossal amount of blood being pumped, which meant my leg was full of blood. I'm just grateful that the artery was untouched.
Video of Gaumont:
View: https://youtu.be/RamvZ6o9EQE?t=40