Overlay and path drawing process for requirements 6 (Interference During Construction), 17 (Weather Effects), and 24 (Existing Transportation Systems). “6+17+24” shows the overlay image of the three requirements; G, at top, is the path diagram marking the darkest areas seen in the overlay image. Alexander and Manheim, The Use of Diagrams in Highway Route Location, (School of Engineering, Massachusetts Institute of Technology, Cam- bridge, Mass, 1962), 17.