I pondered this with HWMBO (a civil engineer) when I first saw the pictures.
The idea of protecting the road surface is a dud, road surfaces are dead cheap; it has to be something more.
The wing walls appear to have been demolished so it may be to help restrain the embankments. There is the possibility of the ground moving if tunneling is to pass under the area, possibly with the bridge supports moving apart and the span then dropping into the gap; smaller gap, less damage.
My personal thought was that its one way to stop over-height vehicles going that way as a short-cut.