At some security checkpoints around New York there is a kind of barrier whose name I'm interested in learning. I've attached two images.
The barrier is a sheet of metal raised a foot or two on one side. If a vehicle is approved to enter, the sheet of metal can be lowered to be flush with the street. (Prior research: I've tried extensive search-engine searches with text and these images. I'm not sure if there's a better SE forum to post on, but Travel seems the closest.)
What is this called?