This 2017 thread documents researching and modeling a distinctive bridge type that survived longer on the B&M than anyplace else, as far as I know:
12-Feb-2017:
The Boston & Maine used wood for many bridges into the 1920s. Our Library of Congress' Historic American Engineering Record documented a couple (links valid 5/2025). This one still stands AFAIK:
http://www.loc.gov/pictures/item/nh0283/
This one in Arundel, ME was replaced in 1995, but it's a better example to follow for the Chipman St. overpass west of Bexley Depot on my B&M Eastern Route layout:
http://www.loc.gov/pictures/item/me0275/
The Sinnott Rd. (Meetinghouse) bridge from railroad west (Boston side):

The signal bridge stands but is unused - 8 years later I still need to photograph it.... The end of one of the enclosed trusses:

One of the angle braces keeping the skewed trusses from folding up or falling over and collapsing:

I wish I'd known where this was in 1990; when I cross its replacement I'm about 5 minutes from Seashore Trolley Museum.
12-Feb-2017:
The Boston & Maine used wood for many bridges into the 1920s. Our Library of Congress' Historic American Engineering Record documented a couple (links valid 5/2025). This one still stands AFAIK:
http://www.loc.gov/pictures/item/nh0283/
This one in Arundel, ME was replaced in 1995, but it's a better example to follow for the Chipman St. overpass west of Bexley Depot on my B&M Eastern Route layout:
http://www.loc.gov/pictures/item/me0275/
The Sinnott Rd. (Meetinghouse) bridge from railroad west (Boston side):
The signal bridge stands but is unused - 8 years later I still need to photograph it.... The end of one of the enclosed trusses:
One of the angle braces keeping the skewed trusses from folding up or falling over and collapsing:
I wish I'd known where this was in 1990; when I cross its replacement I'm about 5 minutes from Seashore Trolley Museum.