The sharp decline has confounded efforts by urban planners, who over the years have tried to encourage the practice by setting aside highway lanes for car-poolers, as well as offering incentives like discounted parking.
They thought they were getting some help from amendments to the Clean Air Act in 1990 that would have required many companies to develop plans to increase car-pooling and mass transit use. But Congress, after hearing from critics who said the proposal was unworkable, scrapped the idea in the mid-’90s.
Today, advocates point to the increase in social networking tools that would make it easier to identify potential ride-sharing mates — yet the national car-pooling rate continues to fall, and today it is below 12 percent of all drivers.
The drop has occurred in cities across the country. For example, the car-pooling rate fell by more than half since 1980 in Rochester and its suburbs, as well as in Worcester County, Mass., and in the suburbs of Kansas City. Even in San Diego County, Calif., the state where modern car-pooling began, the rate was down by more than a third.
Here in the fast-growing suburbs of Washington, the number of people driving alone has more than doubled since 1980. That is a sharp contrast from a generation ago, when Washington had one of the highest car-pooling rates in the nation, with one person car-pooling for every two driving to work alone. Today, for every one car-pooler, there are six solo drivers. This trend crawls to life every weekday morning before dawn, when a stretch of Interstate 95 turns into a glittering river of headlights moving so slowly that drivers need to leave up to two hours to cover a 30-mile trip.
“Painful,” said a 55-year-old accounting firm employee who tries to pick up other riders at designated places in Woodbridge so she can use the restricted, faster lanes.
“Books on tape, music, it doesn’t help,” she said about the daily trip (most of the commuters interviewed here asked that their names not be used). “All I’m thinking is, ‘Oh, God, this is going to hurt.’ ”
The grind of the drive provokes such frustration that commuters do odd things to stay calm. One commuter waiting for a ride at a meeting point here said that one driver had become notorious among the regulars — “the puppet guy,” who apparently used hand puppets to act out arguments to manage his anger over being stuck in traffic.
The population of the Washington suburbs has exploded in recent years, up by more than 60 percent since 1980. Still, the congestion has not served as an impetus for car-poolers, whose numbers, as a portion of all drivers, have fallen.
In fast-growing Prince William County, where Woodbridge is located, the number of car-poolers has actually grown, but not nearly as much as number of people driving alone, which has tripled since 1980.
The census data also show that different races car-pool at different rates. According to the census, black, Hispanic and Asian commuters car-pool far more than white workers.
In 2000, the car-pool rate for Hispanic workers was 28 percent, double the rate for whites, partly because of new immigrants sharing rides to jobs at construction sites or factories. But even Hispanics are relying less on group rides: by 2009, the rate for Hispanics had fallen to 19 percent.
“As cars became more affordable and life became easier, the big car pools broke up,” said Alan Pisarski, a consultant who studies transportation trends.
Car-pooling first cropped up as a policy idea in the United States in the 1940s, when oil and rubber shortages limited the use of personal cars, according to Erik Ferguson, a professor of urban planning and the author of a 1997 article called “The Rise and Fall of the American Carpool.”
Car-pooling was first seriously studied by academics and urban planners in the 1970s, the decade of the oil embargo, “a time of great hope for car-pool enthusiasts,” Mr. Ferguson wrote.
Lew Pratsch, who organized shared rides for federal workers while working for the Energy Department in the 1970s, remembers that decade as a golden era for car-pooling, when big companies like Xerox and Chevron organized car pools for their employees. He picked up his future wife on their first date with a car-pool van.