IT'S HARD TO BELIEVE that in the late 1880s, Bannock, Mont., was one of the fastest-growing, most wildly energetic communities in the West. The mining town was even proposed as the territorial capital. Today, it is a ramshackle collection of abandoned buildings surrounded by mine tailings and open only as a quiet tourist attraction. It takes a powerful imagination to conjure up the place once considered the metropolitan hub of Montana Territory.

Or take Cisco, Utah, once a bustling little town serviced by highway and railroad, but then bypassed by Interstate 70. It now features a landscape of scattered and decaying buildings.

Throughout the West, from the Yukon River in Alaska to the farming service centers of west Texas, mining camps and once-vibrant towns have decayed into relics, their fates sealed by the whimsy of economics, changes in transportation, or the boom and bust of resource extraction. We drive past, wondering what they once were like, or wondering who lives there now, or, perhaps, not noticing them at all.

Which of today's thriving towns will become the next century's ghost towns? What places will have become forlorn, decrepit and abandoned? This might be wild speculation, but could the answer be the West's sprawling subdivisions that depend on the automobile and cheap fuel, those far-flung developments miles from Main Street, work, schools and soccer fields?

What if, over the next generation or two, we wean ourselves from the automobile? What if gas goes to $10 a gallon or more? What if we decide that fighting traffic and spending 15 percent of our adult lives sitting in the driver's seat isn't such a spiffy trade-off for a bigger lot and better view? What if we decide that being married to our car isn't such a terrific deal?

A century from now, the idea of living 10 or 20 miles from town and from most everything we need to do in a day might become an alien and unpopular concept. Instead, Americans might start tightening their embrace of communities, packing in closer, living where everything from the public library to the office is within easy reach.

Sound far-fetched? Maybe. But remember, just a century ago there were only a few miles of pavement in all of America, and though cars were coming on, horses were still our main mode of transportation. The infrastructure that bloomed to accommodate the automobile and gasoline industries - the pipelines, service stations, bridges, highways and interstate system - all came into existence in a few frenzied decades during the last century. Before that, the idea of living far from your occupation, your school, your community, was foreign indeed.

It could be so again.

In fact, I think the shift is already starting. Imperceptibly, perhaps. And yes, I know, subdivisions still sprout across former farm fields and wild landscapes, willy-nilly. People still succumb to nuptial agreements with cars.

But at the gas stations where folks shake their heads while dropping $50 or $75 dollars on a tank of gas - the same tanks they filled only a few days earlier - and at the busy city intersections where motorists fume and sputter with frustration, and will do so again tomorrow and the day after that; and at home, after a busy week, when suburbanites reckon with the reality that they spend maybe a fourth of their time in the car just doing errands and maintaining their lifestyle; at all those place and others, people are considering how their commuting time might have been spent playing with the kids or reading a book. In all those places, the wheels are beginning to turn, the mental light bulbs are flickering on.

This is an insane way to live! That's what people are thinking. They may not be in a position to do anything about it yet. They may not be desperate enough to actually make the leap. But I'm telling you, they're not fools. It's dawning. Give it another decade or two, and you'll see. The subdivisions will empty, house by house. Windows will crack and fall out. Roofs will sag. Driveways will heave and blister in the heat. Weeds will sprout through the concrete. As in Bannock, Mont., it will be very quiet.

Alan Kesselheim is a writer in Bozeman, Montana.