there's a new term for bridges, "orphan", the ownership of the bridge is “legally indeterminate”. There are 81 orphan bridges across Connecticut.

“Orphan” bridges carry municipal roads over railroad rights-of-way not owned by the state.

In Connecticut, “adopted” bridges are those the DOT fully maintains, typically spanning state-owned rail lines. 

In general, an orphan bridge carries a municipal road over a rail line and was once owned by a railroad company but is no longer kept up by such a company

Maintenance work on orphan bridges is divided between the state and the municipality where the span is located. While the state maintains the structural components of the bridge, municipalities take care of its riding surface, including clearing away snow and ice during the winter.

there are 59 overpasses the state DOT has taken full responsibility for — or “adopted” — over the years. They often span rail lines purchased by the state at some point

https://www.ctinsider.com/news/article/ct-bridges-orphans-replace-groton-stonington-21039571.php