But these instances hardly represent the future imagined by Max Schmidt or Robert Heinlein. For one, distances are short. For another, speeds are relatively slow; the American Society for Mechanical Engineers mandates a maximum speed of 4.57 meters per second, though for various reasons, including legal liability, that speed is rarely approached. Another problem is sheer ergonomics—the walkways have to ramp up to speed with minimal "upsetting effect." As a study in the journal Transportation Research noted, "conventional moving walkways have a constant transport speed of approximately half of the maximum pedestrian walking speed. Their speed-range of 0.5–0.83 [meters per second] is considered low, sometimes resulting in a low level-of-service and passengers' impatience." This speed can be improved by actually walking on walkways, but many don't seem to; Jerry Seinfeld singled out for opprobrium "the people who get onto the moving walkway and just stand there. Like it's a ride. Excuse me, there's no animated pirates or bears along the way here."
And as at least one study ("Optimal speeds for walking and running, and walking on a moving walkway," by Manoj Srinivasan, published in Chaos: An Interdisciplinary Journal for Nonlinear Science) has argued, moving walkways can actually result in lowered travel speeds versus normal walking, because of the congestion caused by people standing. (To counter this problem, the "pallet width" of moving walkways, as it known, has actually gotten wider, which allows walkers to pass people with luggage carts.) Even when one is alone on the belt and can walk without interruption, however, the time savings is on the order of a mere 11 seconds over a bit more than a football field's worth of travel. There is also the larger question of whether we want to engineer yet another form of physical activity out of our lives.
Some have begun investigating so-called "accelerated moving walkways," which would promise higher speeds (some three times conventional walkways) over longer distances. The speeds, in addition to the constantly available nature of moving walkways (eliminating wait time), would presumably offer benefits over other forms of transportation. But as was demonstrated by the case of the Trottoir Roulant Rapide—the higher-speed (11 kph) walkway installed in Paris' Montparnasse station—the world doesn't seem ready. (As Collins notes, it was troubled by design and maintenance issues and was taken out of service last year and converted into a regular walkway.)
The Trottoir Roulant was largely viewed as a boondoggle, but it was trying to meet a real need—one that will continue to be an issue for increasingly crowded cities—a need that the project's manager described, in almost DeLillo-esque terms, to the BBC: "The real problem nowadays is how to move crowds," he said. "They can travel fast over long distances with the TGV (high-speed train) or airplanes, but not over short distances (under 1 km)." In other words, in an age of mega projects and mass travel, the trek across the airport can take as long as the trip to the airport.
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