Ice roads (ice crossings, ice bridges) are frozen, human-made pathways on the surface of bays, rivers, lakes, or seas in polar regions. They link dry land, frozen waterways, portages and winter roads, and are usually remade each winter. Ice roads allow temporary transport to areas with no permanent road access. Seen in isolated regions of northern Canada, Alaska's Bush, northern Michigan and Wisconsin, northern Scandinavia, Estonia, Northeast China  and Russia, they reduce the cost of materials that otherwise would ship as expensive air freight, and they allow movement of large or heavy objects for which air freight is impractical.