Ten months in the making, I've finally completed my Eisenhower Interstate System one- and two-digit highway interchange abstraction map! I originally saw Chris Yates's simplified version (www.chrisyates.net) on Strange Maps (strangemaps.wordpress.com), and decided to do a decidedly non-simplified version. If I counted the number of hours devoted to this, it would provide a quantified measure of how nerdy I am. The total hour count is easily in the three digits.
I like the look of Chris's map better than mine (www.chrisyates.net/reprographics/index.php?page=424), but you need to make aesthetic compromises when you're cramming that much information into a small space. Plus I don't want to step on any artistic toes.
Just for kicks, I added lines indicating coastlines and borders.
If you see any inaccuracies, let me know! With over 220 interchanges, I'm bound to have made some errors.
I collected my data using Google Earth, and frequently used the City Boundaries and Places of Interest layers to pinpoint exact locations of interchanges. In places of ambiguity, I applied a consistent set of rules for determining in which city an interchange occurred; these criteria are too numerous and boring to list here, but I'd be happy to explain them if you disagree with my choices.