So I designed this Double deck Bridge. Its 80 feet to the upper rails, and 20 feet from the ground on the lower track with the clearance of 18 feet from the lower rail to the third sill. It might work or it might not work but I'm going to build it as soon as I finish the two level Bridge. the spec. I use are from various wood trestle bridges that I found on the Internet. I wish I could find more spec. on building these type of bridges because I'm into the steam age in model ing railroads.