All in the same family, they raise the pavement three to four inches. They are comparatively inexpensive. Effective in cutting down speed. Make drivers think about their roadway. Also noisy, aggravating and tough on emergency vehicles.
Rotaries are larger versions used at major intersections.
Both can be attractively landscaped. Keeps traffic flowing. May confuse motorists and make pedestrian crossing more difficult. Bicyclists sometimes find them difficult to negotiate. Chicanes, bends or deviations.