I've been over two of them when I was in the USCG stationed in Groton and New London, CT (assuming that is the Thames River). Its the only place in the world you can watch submarines go up the river to spawn, lol.
I've probably made several bridges close to the RR bridge so modifying one shouldn't be too big a job. Need photos and basic dimensions.
Overall length, length of the individual spans, height above the water, number of tracks (probably 2), and so on.
Photos of the individual spans, piers, and ends.
The highway bridge is more then a bit of the problem because it isn't flat. I may have made something similar and could modify it but it would be flat.
Ben