What line is it?
Picture: http://www.nytimes.com/imagepages/2013/07/19/us/HEROIN-3.html
Article: http://www.nytimes.com/2013/07/19/us/heroin-in-new-england-more-abundant-and-deadly.html?pagewanted=all
I rather suspect that that's a boulevard-wide road overpass. Check along the Springfield Terminal Railway alignment in Portland for possible sites.
Chuck