Just a crazy thought, which probably should be in the Crazy Highway Pitches thread: Why not one new bridge halfway between the two bridges (and of course demolishing the two existing bridges)? This would require some extensive expressway construction along both sides of the canal to connect the one new bridge with the existing Rtes. 3 and 25. New roads and bridge are shown in red:
That straight, fat power line ROW was considered in the 1970's for an extension of the MA 25 expressway to the Route 6 expressway, but that would've entailed a third interstate-spec crossing rather than a decomissioning of the existing bridges. It died when the final S-curve alignment of 25 from East Wareham to the Bourne Bridge got bogged down in community opposition. I much doubt you could swing a 1-for-2 bridge replacement. That's just way too little redundancy for a critical region.
Wow I had never realized how perfectly route 25 lines up with route 6 and how it even has a power line right of way already there.
