A causeway is a road or railway route across a broad body of water or wetland raised up on an embankment. Some causeways may only be usable at low tide and the distinction between causeways and viaducts can become blurred when flood-relief culverts are incorporated in the structure; a causeway is however primarily supported on earth or stone, whereas a bridge or viaduct is mainly supported by free-standing columns or arches.
1. Great Salt Lake Causeway, USA