Aleks points me to this map (link from here) showing subway ridership using line widths.
It’s fun, and it would be good to do something similar with road traffic using available data. The statistical problems would be interesting too: road traffic data are incomplete, so you’d want to do some modeling to get reasonable numbers over time. This could be a great project, actually.
My only comment on the subway graphs is that the B and D trains seem to have disappeared below 145th St.:
Maybe their lines could be run parallel to the A/C on the graph? There’s a similar problem with the E/F in Queens. Also it looks to me like two of the 1/2/3 lines have disappeared below 96th St.
P.S. More here.
I really enjoyed this also, but since they are only using data for stations and have no plausible model, using line widths leads to misinterpretation I think. I'd prefer using bubbles with colored, fixed-width edges.
I think the data is the number of people entering at each station, not the number of people riding the lines between each pair of stations. That's why Queensboro Plaza, which has very crowded trains, shows so little activity. Most everyone going through that station, or transferring at that station, is coming from somewhere else. I agree though — the colors are a little confusing…
Agree with the previous 2 comments. This is a classic case of a designer throwing intellectual honesty to the wind for the sake of making a pretty but meaningless picture.
I assure you that they were actually plotting link loads, the picture would be completely different (eg: http://www.caliper.com/TransCAD/TCTransitAssign.p… )
I agree with the first two comments too, but I wouldn't have known about the subtle distinction between gate counts and link loads if Sha hadn't made his version of the chart in the first place.
I think Michael Frumin is being a little harsh. I don't think that it's fair to call the graphic dishonest – that implies malice where there isn't any. (Yes, like the graph implies flow where it shouldn't). This isn't a competition, we're all learning here… though not everyone is studying transit at MIT. I think there's room to be more constructive and certainly more polite.
I note that no particular explanation of the data is given at http://frumin.net/ation/2009/05/spark_it_up.html – a little note (which would also explain the choice of sparklines for a static map) might have avoided the "wrong" message being presented by others.
Disclaimer: Sha is a colleague of mine, and I commented on an early version of his map without thinking much about the data itself. So naturally I'm a bit defensive.