what material to scratch build an 0 gauge overpass?

I have planned a 40" long 0-42 curved overpass over an 0-54 curve. The longest unsupported span is 12". The width of the overpass ranges from 4 to 6". The layout is luan 3/16" plywood screwed/glued onto 1" styrofoam to steel studs. The thickness of the overpass is critical in that it increases the grade. I plan a 5 7/8" vertical clearance. Home Depot has rather rigid clear 3/8" ash, a wood that I have not worked with. any suggestions?

Huizc, I’ve worked with Ash and can’t complain, it’s kind of like oak in the respect that it’s hard and grain is similar. oddly enough it has a dry soap bar feel to it and it’s saw dust. If it were me though I would use Poplar instead due to tighter grain(eaiser to paint and weather) ash’s more open grain pattern is more likely to show through with out added prep work. poplar is harder than pine in the fact that it resist denting and scratches as much but i real easy to work with, cut, sand etc. Hope this helps.

Aluminum bar stock on edge, bent the appropraite radius; like spline sub road bed, with aluminum angle bracket, drill, tap and screw.