I think the drop is quite small and probably no more hazardous than hitting a normal speed bump at high speed. Apparently, they are used in Sweden, with one of the benefits being that they are not triggered by emergency vehicles, which I guess is a great benefit. All in all, though, I think it's probably too expensive to install and maintain. Apparently, they are being used overseas.
https://www.york.gov.uk/downloads/file/2037/annex-b-actihump-leaflet