This is BART’s security camera.
There are two on every train, both mounted to the ceiling above you, I took this shot while standing face-to-screen with it. Although tapered in the back, the front of its all-metal chassis hangs down about four inches, approximately at the base of my skull. I try to avoid standing by this would-be cranium crusher but it’s near the front doors, and during rush hour that’s usually the only space available.
At least twice a week my head is right in front of the screen, providing BART’s security video team with 15 solid minutes of total darkness. I assume one day there will be a violent jolt of a train braking, and they’ll wonder why the footage suddenly turned red.