I feel like this should be something possible with the better looking bridges, the support beams don't allow anything the pass through them though as of its a solid in the center.
#Stack Suspension Bridges over Tracks/Paths
ripe lintel
wooden jetty
and double decker bridges
still carbon
This! Posted something similar. I'm hoping they add support for bridges designed specifically with this in mind, maybe even as convenient a feature as being able to use the upgrade tool with metro or rail tracks on the bridge to add them with a proper model. #1169437813901643878 message
ripe lintel
I would love if it was an upgrade or preexisting bridge to select