A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In the United States, it is used as an equivalent term to controlled-access highway, or a translation for Autobahn, autostrada, autoroute, etc.

In civil engineering, grade separation is a method of aligning a junction of two or more surface transport axes at different heights (grades) so that they will not disrupt the traffic flow on other transit routes when they cross each other. The composition of such transport axes does not have to be uniform; it can consist of a mixture of roads, footpaths, railways, canals, or airport runways. Bridges, tunnels, or a combination of both can be built at a junction to achieve the needed grade separation.