“A highway is any public or private road or other public way on land. It includes not just major roads, but also other public roads and rights of way. In the United States, it is also used as an equivalent term to controlled-access highway, or a translation for motorway, Autobahn, autostrada, autoroute, etc.” — Wikipedia, article : Highway
Taking the highway can often lead to the most efficient route, although it depends on you definition of efficiency. If you consider ecological purposes it could even lead to the less efficient route.