I have several bridges on my layout. I will be showing them here.
This is a double track concrete bridge I scratchbuilt, starting off with a sheet of styreen.
4 square 5mm holes where styreen strip will go through.
8 round 3,5 mm holes for the round beams.
Different view
5mm styreen with 3,5 mm holes drilled, then bent through the square holes, 3,5 mm round beams stuck through the holes in the bridge floor into the holes in the 5mm beam.
Different view
Different view
Abuttments made with H0 scale brick to look like N-scale concrete blocks, the 5mm Beam is supported by the abuttments
Different view.
After painting with, acrylic mixed with powders to get a concrete texture ( difficult to see in the picture).

These are the parts for a set of buildings under the mainline into Kansas City, I know Kansas City didn't have a Highline but need to make this on acount of space. .
I used styrene strips to make the beams and pillars for the structure of the highline , I then painted sandpaper 180 grid to a stuco color using artists acrylics, cut out the places for the Tichy and Grandt Line doors and windows.
Other wall.
An idea of what I want with this. These are the backside of the buildings , I won't have to build the frontsides , they won't be visible. I will be detailing the backside so that you know what is in front, deli, pawnshop etc.