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Lies, Damn Lies, and Chicago's Congestion "Problem"

Ted Rosenbaum

Former athlete, full-time engineer. I'd tell you more but I'd have to kill you.

The Texas Transportation Institute's Urban Mobility Report is always good for a few screaming headlines, and this year's release doesn't disappoint. Chicago and Washington, DC tied for the longest commuter delays,* totaling 70 hours per commuter per year in 2009 (the most recent year for data). That's pretty awful, especialy when you compare that to the 64 hours per commuter per year we wasted in 2008.  And since 2009 was a worse year economically, this number certainly won't improve as more people (hopefully) get back to work, many of whom will commute by driving themselves.

Except that TTI's rankings are a crock. When a rough draft of this report came out last year, Chicago's own CEOs for Cities responded: their "Driven Apart" report is the most thorough debunking of TTI's methods I've ever seen.  Briefly, TTI has 2 main ranking systems, and both of them have fundamental flaws.

  1. "Delay Time." Chicago ranks #1 in the nation in total delay hours, but what is a delay? Well, anytime you travel on a highway below 60 mph or on an arterial below 30, you're adding to the delay.  Nevermind that most expressways around here have 55 mph speed limits and arterials are often 25 mph!
  2. "Travel Time Index" This is the one that really rankles, because it produces a score which state DOTs can use like a cudgel to convince politicians to waste taxpayer money on highway capacity increases that never solve congestion problems. I'll let David Alpert of Greater Greater Washington (our brethren at #1) take it away:

Consider two hypothetical cities. In Denseopolis, people live within 2 miles of work on average, but the roads are fairly clogged and drivers can only go about 20 miles per hour. However, it only takes an average of 6 minutes to get to work, which isn't bad.

On the other hand, in Sprawlville, people live about 30 miles from work on average, but there are lots and lots of fast-moving freeways, so people can drive 60 mph. That means it takes 30 minutes to get to work.

Which city is more congested? By TTI's methods, it's Denseopolis. But it's the people of Sprawlville who spend more time commuting, and thus have less time to be with their families and for recreation.

Of course, who needs a hypothetical when there's a perfectly good real-world example of this: according to the report, Chicago and Houston have the same Travel Time Index of 1.25 (which ranks us 5th among very large cities, for the record). However, Chicago drivers only need an average of 13.5 miles to reach work, while Houston's average commute distance is 22.1 miles. We are desneopolis, and that's a good thing.

*Really, Jon Hilkevitch? You're gonna fall for TTI's trap too? I know you saw the CEOs for Cities report back in September--you wrote about it very cogently. So why the regurgitation of TTI's press release now? I'll give you credit for not stooping to repeat TTI's claim that "in the end, there's a need for more capacity" and instead pointing out how much worse it would be if Chicago didn't have good public transportation. But why not mention Driven Apart and say that although TTI is (unfortuantely) the standard, there are serious problems with it? Help make us an informed citizenry and all that, right?



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