Why is the Red Line running a little slow Tuesday, Wednesday and Thursday nights? Probably because these orange-vested types are cleaning out the pipes under the tracks. Metro's repair guys and gals send a little camera snaking down the pipes to look for gunk – I'm not sure if "gunk" is the technical term for it, actually – and they follow it with what looks to me like a giant vacuum cleaner.

"The water in here is really hard and every couple years we have to come clean it out. A lot of trash piles up," the guy pictured above, between the tracks, explained cheerfully. Is this something Metro planned for when they started the line, I wondered. "Nah." So, do they find any good trash?

"Nah." He paused in thought for a moment, then added, "Plastic bags, mostly."