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Traffic rotaries and other speed bumps

Some pretentious folks at the modern theoretical end of actual architectural and engineering construction like to deploy the lofty phrase "the built environment" as they evaluate the results of real practitioners' design efforts.

At the classical theoretical end, the ancient Roman engineer and architect Vitruvius was more straight forward. The work, he wrote, must have three qualities: firmness (no Kansas City hotel sky-walk collapses); commodity (no multi hundreds-of-dollars-per-square-foot donor named collegiate extravagances), and delight (no Frank Gehry randomly distorted crushed-tin-can appearances).

Neither Vitruvius nor the modernists theorized about the role of user behavior, although it was the basis of Coliseum design then and Yankee Stadium now, just as roadusers were design factors in both civilizations-then and now.

Consider the Roman-road speed bump: typically misidentified as pedestrian crossing blocks on such arteries as the Appian Way. It's hard to believe that they were so closely-spaced and built nearly a foot above the traveled way because of road-mud or trash depth, and easier to believe that their height and close spacing were engineered to cause proto-NASCAR charioteers to reduce speed and steer carefully for the narrow gaps to prevent embarrassing and expensive wheel destruction.

Getting mobs of pedestrians into and out of a venue is a problem different from getting individual vehicle drivers to their destinations without killing each other or wrecking their mechanized (or not) chariots, but it shares the necessity of guessing how courteously (or not) their human design-users will behave toward each other. That's a tougher guess in highway design than in stadium design; the latter hasn't changed much in two millennia; in the former, designers still don't know and can't reliably predict how members of the modern civilization will conduct themselves.

When John Keats wrote "The Insolent Chariots" in 1958, his complaint wasn't entirely that highways were paving over too much grassland; it was also that motorized-chariot drivers weren't nice to each other. Starting in the '20s and '30s, when motorized vehicle were replacing horse-drawn ones on a large scale, highway designers couldn't predict and design for driver behavior as well as Roman stadium designers could, for pedestrian behavior. Their abilities in the soft-science end of highway design haven't improved since, while their skills at the hard-science engineering end have.

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