Remember monorail? That Jetson-era relic, one step above an amusement-park ride, zipping around airports, hotels, and, yes, amusement parks? For a brief moment in the 1960s, monorail-cars or trains running on or under a single, elevated guide rail-looked like the future of mass transit. But that bright vision was eclipsed by a surge of highway building and, more recently, the rush to build urban light-rail systems. Monorail was written off as a novelty, fine for Disneyland but hardly a serious option.

But yesterday’s dreams are today’s leaps forward. Thanks partly to technological improvements, partly to new recognition of the limitations of conventional rail, and especially to the grassroots activism of impatient citizens, monorail is making a comeback. Today, space-short Japan leads the world in elevated transit, with eight urban monorails. Sydney, Vancouver, and Singapore all use monorails, as do planned communities in Brazil and parks in South Korea. Now monorail boosters in several U.S. cities are vying to make their towns next on the list.

In Salt Lake City, those boosters recently attempted to persuade transit officials to build a monorail in place of a controversial planned light-rail system, on the grounds that light rail would eat up too many precious street lanes. That effort failed, but monorail boosters have made more headway with the Ohio-Kentucky-Indiana Regional Council, which has proposed a new light-rail system for the Cincinnati metropolitan area. Vexed because light-rail vehicles can’t handle the grade to the regional airport on their side of the Ohio River, residents of Covington, Kentucky, are pressing for a switch to monorail, whose rubber tires and enclosed guideways provide better traction than steel-wheeled light-rail vehicles. They’ve persuaded their congressman, Jim Bunning, to arrange federal funding to study the monorail option.

But it’s Seattle, home to the mile-long monorail left from the 1962 World’s Fair, that has given the technology its broadest endorsement. Last November, Seattle voters approved a 42-mile monorail system running to all four corners of the city, over the opposition of city officials and the business establishment, who favored light rail and buses. The ballot measure was an unusual exercise in do-it-yourself transit planning, drafted and promoted by an activist/cab driver, Dick Falkenbury, who says he got the idea while “stuck in traffic, watching the monorail zip by overhead.”

“Until you get out of traffic, you’re still stuck in traffic,” Falkenbury explains. “Once you realize that, only monorail makes sense.” The fact that most U.S. monorails are at theme parks and other private venues only proves the technology’s efficiency, he insists: “When you build with other people’s [i.e., public] money, you build light rail. When you build with your own money, you build a monorail.”

Even monorail’s critics concede that, because it weighs less, it can be elevated less expensively than rail. Elevated systems can be built quickly; because they needn’t tango with traffic and pedestrians, they can be automated, eliminating the driver salaries that are conventional transit’s biggest operating expense. (The other way to get trains out of traffic’s way, digging tunnels, is prohibitively expensive-as Los Angeles is discovering.)

Though view-sensitive residents squirm at the thought of a monorail’s elevated guideways blocking their light, today’s guideways are much thinner than 1962’s concrete behemoths. And their pillars are spaced more widely-100-plus feet apart in a leading model from Montreal-based monorail maker Bombardier. Technical improvements have also obviated another longtime monorail shortcoming: awkward switching from one track to another. Bombardier can now switch tracks in 8 to 12 seconds, making multi-track systems feasible.

But why stop with a conventional, mass-transit monorail? University of Washington engineering professor emeritus Jerry Schneider notes that Seattle’s Monorail Initiative would allow the city to implement a truly revolutionary solution: personal rapid transit (PRT). Developed in the 1970s and now being revived on three continents, PRT offers individualized, point-to-point service in private (say, four-seater) cars running on lightweight, computer-controlled, elevated guideways-usually monorails but sometimes dual rails. Variously dubbed “automated taxis,” “horizontal elevator,” or “personal monorail,” it’s the only transit form that just might match the automobile’s convenience, without its environmental downside.

The monorail of the future may surprise even its present-day proponents.