London's Tube map is famous for throwing proportion, distance and scale out the window in favor of user friendliness. Instead of an accurate representation of the geography the Tube passes through, it instead presents an immediately understandable , over simplified, easily readable diagram. Its designer, Harry Beck, was influenced by wiring diagrams that instead of portraying a tangled mess, instead show an organized map.
In Beck's maps, lines run only vertically, horizontally or at 45 degree diagonals. Stations are clearly delineated by dots and interchanges by larger circles.
This map's designer, Cameron Booth, describes the way he adapted Booth's idea to our interstates:
Drawing my cues from the original and best metro diagram, H.C. Beck's wonderful London Underground diagram, I have rendered the Interstate system in a much simpler form. I have made the "major" highways (those divisible by 5) the framework of the map, with the "minor" highways reduced in importance and rendered as thinner grey lines. Even with these highways, a difference in the greys indicates whether they are even-numbered (west-east) or odd-numbered (north-south). Dots on the highways indicate interchanges: large dots where major highways meet other major highways, smaller dots where major meets minor and tiny dots where minor highways begin or end. A full key at the bottom indicates clearly where each highway begins and ends.