A quick (17min) TEDx talk. This is a Schematic design style, focusing on usability by taking into account cognitive load and capacity.
Maxwell Roberts is a lecturer of Psychology at the University of Essex and talks about how today’s designers are struggling to achieve the same clarity and impact of Henry Beck’s original London Underground tube map.
The second link is an article on map effectiveness:
Using the science of peripheral vision to test the Tube map – We know how the brain processes things on the edge of its field of vision, and we can use that to analyse the quality of subway maps.