A shower, a quick cup of coffee, a kiss goodbye (if they're lucky), and they're off. Keys are inserted in ignitions, train doors slide open, feet hit the sidewalk, and it begins: that great mass migration from home to work known as the American commute. In its scale and dynamism, it resembles an awesome natural phenomenon—a volcanic eruption or a flood—but viewed up close, it consists of millions of individuals impelled by private preoccupations. They may move as a herd, but they don't feel that they're part of one as they check voicemail, ponder crossword puzzles, or just doze off. And though they may sense that they're part of something big, much of the time they feel acutely alone, even when the subway car is jammed, the overhead bins of the small jet can't accommodate another carry-on, and the carpool lane is bumper to bumper, backed up behind a wreck. (View Vincent Laforet's portraits of commuting.)

Given these disorienting conditions, commuters may not realize that the patterns of their movements are changing. The trends are subtle in some cases, but they alter our stereotypes about this defining national ritual. As depicted in countless books and movies, from the fiction of John Cheever (the laureate of New York City's Grand Central Terminal and its harried, briefcase-toting company men) to movies such as Falling Down (Michael Douglas goes bananas in L.A. traffic, abandons his car, and shoots a bunch of people), morning rush hour is our cultural equivalent of teatime in Britain.

But nothing stays the same forever. Take the rise of reverse commuting, in which workers swarm outward from cities to suburbs. According to a study of American commuting by professor Alan Pisarski, the frequency of such unconventional trips has more than doubled since 1990. Why? Because jobs are spreading out in much the same way that housing did in the early age of sprawl.

Trips from suburb to suburb, called cross-commuting, are increasing too. Often these treks bypass the urban cores that, in the old days, would have been their target. This conjures up the image of two skylines standing way off in the distance, seemingly obsolete, while thousands of travelers ignore them, bound for less cluttered horizons. Of course, the landscapes we commute across are also changing. As dairy farms are converted into semiconductor assembly plants, places that were neither here nor there are becoming economic hubs, with parking lots where feedlots used to be.

Another new trend seems to defy the climbing price of oil as well as the human body's need for rest: the upsurge in "extreme commuting." The number of us who spend more than 90 minutes in the limbo of neither-home-nor-work has grown twofold since 1990. Spending hundreds of dollars on gas each month clearly strikes a lot of people as a good deal when it means smaller mortgage payments. And it's an easier deal to make now, given the advent of satellite radio, smartphones, and other devices that allow commuters to fill what used to be dead time with lots of electronic sound and fury, and maybe even get some work done before the workday has properly commenced—or after it has allegedly finished.