In combination with the LGV Nord, it has also impacted international journeys to other cities in France and to London, ensuring high-speed through-running by Eurostar, TGV, Thalys PBA and Thalys PBKA trainsets.

At Halle (km 13), the HST tracks split from the mainline and enter their own cut-and-cover section before crossing the Brussels–Charleroi Canal; at km 17, the high-speed line proper diverges from the mainline at the Lembeek Viaduct, supporting 300 km/h (190 mph) speeds.

Between Rebecq and Enghien, the line parallels the A8 motorway, separated by a security fence.

Slightly further on is the 2,005 m (2,193 yd) long Arbre Viaduct (one of the longest rail viaducts in Europe) between Ath and Chièvres; it passes over the Ath–Blaton canal, the Dender River, the Mons road and the Ath–Jurbise railway.

Eleven kilometres (7 mi) further on, the Frétin triangle splits the LGV Nord towards Paris or Lille.