How Viscous is a Car?

Taking time tonight to wonder at the complexity and ingenuity that lies behind the American Interstate Highway System.

According to the website for AASHTO (the American Association of State Highway and Transportation Officials), and a summary of their publication "A Policy on Design Standards - Interstate System" found on Wikipedia, the initial notion of an interstate system goes back to the early 1930s. Studies commisioned under Franklin D. Roosevelt evaluated the nation's needs, and Congress' 1944 Federal-Aid Highway Act enacted those reccomendations, leading to the development of a complex, evolving, but universal set of standards for America's interstate highways. These standards relate to access, speed, grade, lane width, sloping, recovery areas, curb slopes, vertical and horizontal clearances, and bridge strength: all elements the seem to evoke the image of some sort of high-speed aqueduct system.

This, in turn, invokes comparison to the feats of the Romans; and it seems like something they might have done had they had the ability. A system mandated by government and controlled by public standards, based conceptually around the science of fluid dynamics, supported by the discipline and aesthetics of architecture, and realized through the advanced technology of modern large-scale construction.

But one sticking point I've noticed, the Achilles heel--if you will--in this awe-inspiring system, has to do with viscousity. You see, no matter how detailed the fluid models used by the designers of the interstate, no matter how many times they measured and analyzed the behaviors of liquids around a bend of a certain degree or down a shoot of a certain angle, they could never quite account for the fact that cars and trucks do not have the same viscousity as H2O. And, unlike H2O molecules, cars do not all behave in the same way: not individually, not as a group, and not in relationship to one another.

What does this mean? It means that in execution, the entire vision has been diluted. Some people move way too quickly entering from a weave lane, startling and endangering the exiters. Some exit too slowly or cautiously, upsetting and frustrating the enterers. Some cars want to move just too fast altogether, and unlike water, this has nothing to do with gravity, or depth, or degree of approach. Some cars (and some drivers) feel the weave in the road more than others, swerving through corners almost erratically. Others feel safe drifting across lanes through a pronounced turn, which can be quite upsetting to other cars, who might balk, slow down, switch away quickly, or even accelerate in response.

Ultimately what this means is--even though we find it incredibly exciting to watch water charging through rapids, drifting along wide-banked flows in the flatlands, and speeding around the bends in a narrow, hard-rock river, even though we gain such excitement from riding this flow and from watching the waves crest and the current froth as water collides with water--it is far more exciting, far more dynamic, far less predictable, and far more dangerous to watch a mass of cars streaming along the interstate.

And better yet to be driving in one of them.

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