Sentence:  We cannot and should not be rebuilding old "two lane" sections of the air transport system with segments having "eight lane superhighway" capacity without knowing the full economic, safety, and environmental impacts of the entire air traffic <WSD>superhighway</WSD>. 
Meaning of the word marked with <WSD> tags:  A major route that carries most of the traffic going in a given direction by a specified mode of transportation.