Like Water: Traffic "flow" betrays science

Jane Jacobs continues her war of words on analogies, or, what I prefer to call guiding metaphors. I first mentioned her distaste for such methods in the introduction to The Death and Life of Great American Cities and that book’s chapter on “The kind of problem a city is.” Here, in “Science abandoned” in Dark Age Ahead, she uses the same analogy that I attacked - that traffic flows like water.

Temporarily divorcing scientific inquiry from its tools, Jacobs establishes four steps of the scientific state of mind, absent the jargon used in the steps of the scientific method as you employed it on your fifth grade science fair project:

1. The fruitful question
2. Frame a hypothetical answer
3. Test that answer (or observe real world tests of that question, as in social sciences)
4. Ask more fruitful questions based on findings

Technology-based “How?” questions can mess with the order a bit. The hypothesis can come after the testing and evidence. Jacobs identifies the “late-forming hypothesis” that can be a major surprise. Continual feedback, when given proper attention over the course of this inquiry, guides one to surprise, despite the entrant’s expectations.

If I can add some insight to Jacobs’ outline, sometimes the technology comes before the question. Or, as some of my favorite tech pundits have put it: “A solution looking for a problem,” referring to the Amazon Kindle. The question then becomes, “How can we use this technology?” For snappy web applications, the question becomes, “How can we monetize this?” See twitter.

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Science is abandoned because we are human. In the most formal/technical use of the word, it’s ramifications, that is, the branching out of all the consequent erring answers compounds the costs pseudoscientific answers.

We’re human. Even the scientists are. Our identities are bound up in our worldview. For scientists, they’ve invested careers and staked their authority on the prevailing scientific paradigm. This can trip up any of the steps listed above - especially when it comes to observation and data analysis from step 3. If the inquiry falters there, no good feedback results from step 4. A given branch of science stagnates.

Jacobs continues lashing out at the traffic engineers and highway builders of the 1950s. Death and Life was not enough. The myth of traffic flowing like water continues. Traffic models err.

The unquestioned assumption: traffic remains constant. If a road is closed, traffic must find other routes, increasing congestion.

Traffic planners create impenetrable models based on this error. Their “studies” perpetuate this fiction - not tested in reality.

You can see the clash in views trickles down in the comments (1, 2) about the closing of major thoroughfares to automobile traffic, including Times Square.

Traffic planning/engineering may be turning a corner. I’ve mentioned Tom Vanderbilt - chronicler of traffic planning and engineering, who has also sounded off about the Times Square closing. He also blogs. I also have great hopes for folks like Todd Litman of Victoria Transportation Policy Institute (VTPI) and Donald Shoup, author of The High Cost of Free Parking. The paradigm may be shifting.

Tomorrow, I’ll go back and look at the paradigm of my own credentialed profession as another example of a profession that’s stuck in a bad paradigm.