In reference to traffic decks - here's a pic of the traffic deck over Seymour St. for construction of Granville Station
which has a ticketing hall directly under Seymour St.. I remember that the deck itself was made of heavy wood timbers.
on Page 24 of the Transit Museum Society SkyTrain Gallery.
https://transitmuseumsociety.org/wp/photo-albums-skytrain/
https://transitmuseumsociety.org/wp/photo-albums-skytrain/