Those barriers are definitely permanent, they have expansion joints going through them at each ends of the bridge. They aren't as tall as the bridge parapet walls or a typical "Ontario tall wall". I am wondering if they are only located on the bridge itself as part of bridge code requirements? Could they be in place as part of structural reinforcing of the bridge deck for the load of trains?
**EDIT**
Looking at the cross section a little closer, it looks like the road surface on each side of the ROW will be higher than existing, meaning those "walls" won't be all that much higher than a curb. My assumption is that those barriers simply contain the ballast for the track and won't end up being all that high once completed. Keep in mind this is a bridge deck therefore they don't have anywhere to "bury" anything they normally would otherwise therefore everything appears to be higher compared to the existing bridge deck..... All assumptions of course!
**EDIT**
Looking at the cross section a little closer, it looks like the road surface on each side of the ROW will be higher than existing, meaning those "walls" won't be all that much higher than a curb. My assumption is that those barriers simply contain the ballast for the track and won't end up being all that high once completed. Keep in mind this is a bridge deck therefore they don't have anywhere to "bury" anything they normally would otherwise therefore everything appears to be higher compared to the existing bridge deck..... All assumptions of course!