Seams between systems and the Vignelli NYC subway map

I just read “Mr. Vignelli’s Map” by Michael Bierut over at Design Observer. In the post, Bierut remembers and analyzes why the public rejected Vignelli’s map of the New York City subway system. (Here’s the Vignelli subway map.)

The Vignelli map smartly acknowledged that for passengers of the subway focused on navigating the subway system itself, above ground geography was nothing but a factor of added complexity. So the map instead was oriented around the subway lines and stops themselves, abstracting actual geography. This was a keen simplification from an information design perspective.

But consider this observation from Bierut’s article.

To make the map work graphically meant that a few geographic liberties had to be taken. What about, for instance, the fact that the Vignelli map represented Central Park as a square, when in fact it is three times as long as it is wide? If you’re underground, of course, it doesn’t matter: there simply aren’t as many stops along Central Park as there are in midtown, so it requires less map space. But what if, for whatever reason, you wanted to get out at 59th Street and take a walk on a crisp fall evening? Imagine your surprise when you found yourself hiking for hours on a route that looked like it would take minutes on Vignelli’s map.

The concept of designing the seams between systems has become apparent within the user experience design community over the last couple years. This is an example of that problem of seams.

Passengers of the subway system are also navigators of the city itself, so their context of use spans beyond the subway and the end of their decisions are not merely which stop to get on and off of, but where they are going once they get out of the subway.

Bierut makes the point:

The problem, of course, was that Vignelli’s logical system came into conflict with another, equally logical system: the 1811 Commissioners’ Plan for Manhattan.

How can designers consider the seams between the subway system and the city plan to result in a better-designed subway map?

NYC, of course, has a functioning subway map. Is functionality the only litmus test?

(I’ve taken the subway in New York City only once, and managed to get from Point A to Point B successfully, although with some anxiety.)