The bags look the same. Aren’t they covering something electrical?
I’m not an engineer or anything, but we do have similar grates in the sidewalk in downtown Nashville. I know ours are electrical equipment. Always hate walking across them.
I’ve also read that the grates have something to do with the subway ventilation system. This makes sense to me too, since right where he was filming/the street shot is right by the Smithsonian subway station at 12th St. SW and Jefferson Dr. SW.
I’m finding them all over the place over the span of several years. Here’s a better view of one of the grates from August 2013. https://tinyurl.com/b8vrjauj