Time scale maps

Maps of travel times have various names, e.g., time scale maps, isochrone maps, etc. Often a geographic map forms the background so that travel time is superimposed on distance traveled. Occasionally, the time scale replaces the distance scale and the map looks distorted from a geographic perspective, but is correct from a travel time perspective. For example, here is the Washington, DC, Metro (subway) map in two forms, the left in geographic form and the right in time scale form:

Here is a map of Europe, on the left in geographic form, then representing rail travel times, and on the right, high speed rail travel times:

Next is an outline of travel times by train from Paris superimposed on an outline of France:

Just as maps of distance show space in two dimensions, so maps of travel time show time in two dimensions.