My case for Frequent network mapping continues to inspire tech-savvy readers to draw their own. Jeff Wegerson, for example, has developed a method of automatic map generation using the same data files that Google Transit relies on. He's tried it out on Chicago. His entire map is here, including technical notes for others who'd like to try it.
The most interesting thing to me from Jeff's work is this nice illustration of the threshold definition problem. Exactly how frequent is frequent? If you say every 7.5 minutes, Chicago has exactly one frequent service, a piece of busline on 79th Street. If you say 15 minutes, you get a network covering most of Chicago.
If you stare at these, there's a lot of information here about how Chicago's transit system really works, information you'd never get from a standard system map or from reading timetables. Who knew that a portion of 79th Street is more frequent than any of the rapid transit lines? Who knew that east-west services on the south side are more frequent than the north-south services there, so that when you draw the limit at 11 or 12 minutes you get a bunch of parallel lines that connect with rapid transit but not with anything else? You can also see easily that the territory of the Orange Line corridor (the string of green dots extending southwest of downtown toward Midway Airport) is a relative dead zone by Chicago standards, supporting north-south 15-minute frequencies but not much better than that, and no east-west lines to speak of.
In fact, as someone who doesn't know Chicago all that well, I'll remember these maps next time I need to visualize the city, becuase they tell me what really matters about the city's patterns of transit demand, which in turn tells me a lot about the city's shape.
As for Jeff's graphical choices: How do you feel about rendering rapid transit as a string of station dots? I like it, as long as it's clear how the dots are connected. In a very dense rapid transit system like that of Paris, it would be chaos, but in Chicago's simple radial rapid transit network is not hard to follow.
Jeff also uses a convention that I've seen in other grid cities but never quite understood: different colors for north-south lines as opposed to east-west lines. Los Angeles used to do this on its maps too. I've always assumed that the purpose of color (and line-weight) in mapping is to convey information that is not obvious from the lines themselves -- information such as frequency and span. But I can see that a north-south line is north-south, so why do I need a color to tell me that?
There's clearly some viral potential in the frequent mapping idea. I've heard from readers who are working on automatically-generated frequent network maps as a business venture. I also had a brief exchange with Google Transit's staff on the subject, and got their standard "we only have so much time" response. So I hope someone makes a business out of this, because if they succeed, Google will probably buy them out, and they'll be set. If that turns out to be you, remember the humble blogger who lit the spark!