Retaining walls with traintrack section on top

Sometimes you want to build a elevated train track started from higher level of terrain which is hold in place by a retaining wall. But you can't build the rail on the same level since it would collide with the retaining wall.
So could we have a special retaining wall with a train section on top. This way, an additional slope on the traintrack could be avoided without some additional terraforming work.
Maybe just add some steel to the costs of regular retaining 2x4 walls for the rails.

It would be nice if train tracks could just go over retaining walls as part of the track support, so can do a dig under without requireing train to go op or pre dig a level down before putting retaining walls.
i.e. make retaining wall double as track supports when needed.