In modern usage, a causeway's a road or railway elevated on a sandbank, usually across a broad body of water or wetland. A transport corridor that's carried instead on a series of arches, perhaps approaching a bridge,'s a viaduct. In the U.S. a short stretch of viaduct's called an overpass. The distinction between the terms causeway and viaduct becomes blurred when flood-relief culverts are incorporated, though generally a causeway refers to a roadway supported mostly by earth or stone, while a… (More on Causeway)