Well, there's always the Cresson Street Elevated in Manyunk. Although, only about 3/4 mile long.... It fits all the requesites for an elevated line. Runs above a street and even has a station. I remember about 5 years ago, when I driving a cab on the Main Line.... I took some Villanova students to Manayunk.... We had to wait curbside for some reason, and A R6 passed over head.... One of the kids said to the others in the car "Kinda reminds me of Brooklyn around here".... Plus those who live in Manayunk also call it the "el"...
Then there is also the PATCO viaduct in Collingswood.... Although you can't drive directly under it.... there are two streets that run parellel to it for a good stretch.
Oh, and how could I forget the old P&W ROW in Norristown.... although you could not technically drive under it, you could walk under it, since it rode above the sidewalk on Swede Street.
I think they have all been mentioned.....
900,000 tons of steel, made to roll
The brakes don't work and this grade's so steep
her engines sure to blow...
900,000 tons of steel, out of control
She's more a roller coaster, than the train I used to know.