There are no footways along the edges of the road, so it isn't a regular bridge.
Because the shadows are from the left, the location is east or south-east of the Atomium.
My guess is the "bridge" is an ornamental feature in the Royal Estate, Laeken Park, but this park has been pixellated in the Google satellite views and there is no detail to be seen.
Edit: did you also ask recently on this page?
I'm looking for information regarding the locations for the Pink Floyd promo films that were made in Belgium, 1968.
which has the following comments
I've studied all the footage, and to me it looks like the "Scarecrow" and "See Emily Play Locations" are part of the same area, and the "Paint Box" location may be above them. I can see concrete stairs in the "Emily" film that I'm guessing may lead to the "Paint Box" location.
Apparently, the footage is filmed on the remains of the exhibition '58, under the bridge, near the American Theatre. I've checked on google maps and it looks like the American Theatre is gone but the base is there. I can't find the bridge from the "Paint Box" film, or the oval pool with the ornament in it, as seen in the "Scarecrow" clip. I'm wondering if these 2 locations are sadly long gone.
Update: following comments and answer from @Some wandering yeti.
At the beginning of the video, you can see the alignment of the "bridge" with Atomium, specifically, with the three spheres in the layer below the single top sphere. So there are only 3 possible directions the location can be from the Atomium, and with Google Earth 3D projections I can see the most likely is from just south of east.
I can't get low enough for the right height, but this shows the angle, and the tower blocks (cropped here) are seen on the actual view.
So, searching for a curve of road from the maps there are two candidates, and close to one is this square, which although not the actual location is built in the similar style to the "bridge".
You can't see the Atomium in this view: the trees have continued to grow since 1968.