This neat video showing various railfan excursions from the 1950s to 1970s in the DC area shows a wide variety of subjects, including a brief, rare color film shot of the trolley approaching its crossing of the B&O’s Georgetown Branch, which crossed the trolley tracks on a deck girder bridge. The trolley last ran to Glen Echo on Jan 3, 1960 and the area beneath the bridge would be filled in later that year. (I walked the line back in 1991 and witnessed this deck girder bridge sitting only a few feet off the ground. It was a strange sight.)
Video begins at the 5:54 mark and is only a few seconds long, but it’s neat to see. In the background you can see the GB bridge crossing over the tracks. There was a second deck girder bridge to the left which extended the crossing.