This is a tactile warning device, also-known-as truncated domes. Truncated domes are a much better description since they actually are domes with their tops cut flat. They are meant to be a warning to anyone stepping on them or rolling over them that they are about to enter a street or parking lot.
However, the word tactile means a sense of touch. Unless you are down on your hands and knees, running your hands across the truncated domes, you’re actually feeling them (through your feet or bottom), not touching them. So the phrase “tactile warning device” is not entirely accurate. I just thought you ought to know.