![]() The moving-gas model of traffic reproduces many phenomena seen in real-world traffic. But the physicists added some terms to the equations to take the differences into account, and the overall description of traffic as a flowing gas has proved to be a very good one. Cars do not behave exactly like gas molecules, to be sure: for example, drivers try to avoid collisions by slowing down when they get too near another car, whereas gas molecules have no such aversion. The Germans had noticed that if one simulated the movement of cars and trucks on a highway using the well-established equations that describe how the molecules of a gas move, some distinctly eerie results emerged. SUCH was the happy, practical, and deterministic state of affairs up until a few years ago, when several German theoretical physicists began publishing papers on traffic flow in Physical Review Letters, Journal of Physics, Nature, and other publications not normally read by civil engineers. Find a way to eliminate the bottlenecks and flow will be restored. The mathematical and computer models indicate that when traffic jams occur, they are the result of bottlenecks (merging lanes, bad curves, accidents), which constrict flow. These included "add road space" and "lower the number of vehicles." This would not, as the saying goes, appear to be rocket science.Įven when American traffic engineers have ventured closer to rocket science, with computer simulations of traffic flow on multi-lane highways, the results have tended to reinforce the American reputation for practicality and level-headedness. A recent study funded by nine state departments of transportation to examine the doubling in congestion on urban highways and primary roads that has occurred over the past two decades listed in its final report various ways that traffic engineers have tried to alleviate the problem. As an American academic discipline, traffic engineering is centered in civil-engineering departments, and civil engineers tend to believe in solving problems by going at them head on. ![]() Bigger and better highways are as American as fast-food restaurants and sport utility vehicles, and when it comes to making the crooked straight and the rough places plain, the practicality of American traffic engineers is hard to argue with. The latest field to host this conflict of national styles is one that seems at first glance to offer little prospect of a sporting contest. ![]()
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