Are you thinking just of roundabouts that include a raised middle and/or central reservations on approaching roads? In general, roundabouts need no more space

Are you thinking just of roundabouts that include a raised middle and/or central reservations on approaching roads? In general, roundabouts need no more space and cost than a regular road would, see e.g. https://goo.gl/maps/Y6jzLq5SuYzMMf2a6 https://goo.gl/maps/Y6jzLq5SuYzMMf2a6