One example of distortion that occurs in road maps is that there are some roads which are displayed as "thicker" than would be accurate. Interstate highways, in particular, are represented more thickly than would be correct based on proportion. The added thickness is to indicate a major thoroughfare with no traffic lights. This is a distortion of emphasis. But there are also distortions of representation. Fundamentally, these distortions occur from depicting three dimensional space onto a two dimensional surface. One such well known type of map which manages this representational issue in a clever way is the Mercator map. Mercator maps make land masses nearer to the poles, for example Greenland, appear larger than they actually are. These maps also depict lines of longitude, which in reality are great circles that intersect at the poles, as parallel lines.
Background on Mercator Maps
Examples of Mercator Maps
Does the presence of these distortions render the maps useless? Should we instead focus exclusively on representations that are perfect replicas?