Edward Tufte: Graphic of the Day

Monday, December 29th, 2003

Edward Tufte‘s Graphic of the Day from February 10, 2002 caught my eye — it’s about road and exit numbering. Why did this catch my eye? Well, I’ve been living in Pennsylvania and cursing the horrible freeway — pardon, turnpike — signs for a couple years now, including the numbered exits. Actually, numbering the exits isn’t so bad, but not listing what exits are coming up (and how far they are) is bad. We never had exit numbers in California.

Then I visited for Christmas, and I saw that the Culver exit on the 5 (note to easterners: it’s the 5) is now exit 99! Eek!

Anyway, what I didn’t realize is that some states number exits consecutively, while others number them by distance. Numbering them by distance sounds…useful. And you don’t have to renumber (or use A, B, etc.) when you add a new exit.

Something else I didn’t realize: Pennsylvania is in the process of switching over from consecutive to distance-based exit numbers. Very interesting… (And it would explain all the “old exit” signs…)

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