King Street underpass at the transit hub

[ijmorlan]

Just wondering why they would use ballast on the bridge instead of embedded track. Is this to help disperse the vibration or something totally different?

I believe mainline railway bridges (at least here in Ontario) almost always use ballasted track. As far as I know it’s exactly the same ballast and track structure as everywhere else, just resting on a bridge deck instead of on the ground. Some bridges, I think older ones, have ties as part of the bridge structure and the tracks attached directly. The old Laurel Creek crossing was like that. I can’t say why for sure, but certainly by doing it this way the track construction technique does not have to differ on and off bridges.

Another note: as far as I can tell, the freight trains on the Waterloo Spur will not travel on *any* embedded track. I don’t know if it is more difficult to embed track up to freight specification or for some other reason.