PARIS -- On a recent Friday evening, Vincent Accart maneuvered his 20-year-old Mercedes station wagon through the rush-hour traffic to a rendezvous at a busy fuel station on the edge of Paris. There he met three strangers who hopped into his car for a three-and-a-half-hour drive to Rennes, in Brittany. It had all been arranged beforehand, via the Web.
For more than a year, Mr. Accart has been making the weekly commute to Paris, where he found new employment last year after losing a job closer to his home in Rennes. To amortize the cost of fuel and tolls -- about €150, or $195, for a round trip -- he fills the other seats in his car, using a French Web site that arranges shared rides.
"When my car is full, it covers 75 percent of the cost," he said, adding that moving to Paris was not an option because of the prohibitive cost of housing his six-member family. "I'm not doing it to make money, just to be able to keep my job."
One of the side effects of the European economic crisis is a surge in carpooling, as people from many walks of life seek to cut their outlays on travel. Workers making daily treks to and from the office, students heading home for the weekend and even vacationers chasing the sun are turning private vehicles into the newest form of public transportation. Rising environmental awareness may have fueled the trend.
Paradoxically, the growth of ride-sharing services has given Europe a competitive advantage in one niche of the digital economy, where European ventures in other businesses have often struggled to keep pace with those of bigger American rivals or have simply copied U.S. ideas. Two European companies, BlaBlaCar, based in Paris, and Carpooling.com, based in Munich, are global leaders in ride-sharing. With recent capital infusions from outside investors, they are accelerating international expansion.
"It started out a bit like hitchhiking, but now it's almost like booking a seat on a train," said Nicolas Brusson, a co-founder of BlaBlaCar. "The potential market is huge."
The volume of business is impressive. BlaBlaCar says it arranges 400,000 rides a month -- the equivalent of more than 1,000 French high-speed trains, loaded to capacity. The number of drivers and passengers who have registered on the site has grown from 100,000 in 2009 to 2.3 million today.
Carpooling.com says it is even bigger, with more than a million rides booked monthly via its site and more than four million registered users.
The sites work in similar ways. On BlaBlaCar, registered drivers offer seats at prices of their choosing; the company caps these rates to prevent drivers from making profits on the trips. Passengers pay for tickets online and the company keeps a commission. Carpooling.com also shows fares from partner services like Deutsche Bahn, the German railroad.
Revenue from ride sharing remains modest. Mr. Brusson said it posted about €1 million in sales last year, about $1.3 million, but he added that this total was more than doubling each year.
Accel Partners, the Silicon Valley venture capital firm, recently pumped €7.4 million into BlaBlaCar. Daimler, the German car manufacturer, invested an undisclosed amount in Carpooling.com, whose other backers include a German venture capital firm, Earlybird.
"One thing I like about BlaBlaCar is that it is not a copycat, it is an original idea coming from Europe," said Philippe Botteri at Accel Partners, who sits on the BlaBlaCar board.
With international expansion in mind, both companies recently adopted new names. In their domestic markets, BlaBlaCar and Carpooling.com still operate Web sites under clunkier, local-language names: covoiturage.fr in France, which uses the French word for carpooling, and mitfahrgelegenheit.de, employing the German for "ride-sharing opportunity.")
While most of BlaBlaCar's business is still in France, the company has opened sites in Britain, Italy, Portugal and Spain and is considering other markets. From its stronghold in the German-speaking countries, Carpooling.com has rolled out sites covering much of Europe.
In the next few months, Carpooling.com plans to start its service in the United States, where no ride-sharing site has established a nationwide presence on a comparable scale.
"We are convinced that the United States is a potentially attractive market," said Simon Baumann, a spokesman. "The car is perhaps even more important there than in Europe."
Mr. Brusson, however, said he was skeptical about the potential for the United States, citing factors like a lack of openness to public transportation and lower gasoline costs, which reduce the need to share car journeys. But while Americans have been slower to adopt Internet-arranged carpooling, they have eagerly embraced other kinds of "collaborative consumption," in which individuals use the Web to share, rent or sell their own goods and services.
Airbnb, the fast-growing site that offers short-term rentals of private homes, operates on a business model similar to those of the ride-sharing sites.
While safety and security are obvious concerns for users of such services -- and for the sites that link them up -- BlaBlaCar and Carpooling.com insist that they have systems in place to reduce the potential for trouble.
On BlaBlaCar, for example, drivers have to provide their banking details and post profiles that include information about their cars. Many add pictures, thought they are not required to do so. Passengers can rate the drivers and add comments about the quality of service. Some female passengers choose to travel only with female drivers, Mr. Brusson added.
"It's very rare that we get a story of someone zigzagging at 200 kilometers per hour," he said. If this happens, and it is corroborated, he said, the driver involved is barred.
BlaBlaCar also came up with a quirky way to deal with another potential menace -- garrulous drivers and passengers. One feature, which gave the company its new name, is a "blabla index," which lets drivers specify the amount of conversation they will tolerate.
Jerome Lefloc'h, who was traveling to Rennes with Mr. Accart to visit friends for the weekend, said he enjoyed the social interaction that could spring from sitting with strangers for a few hours.
"It's a lot cheaper than the train, and more pleasant, too, because you can talk to the other people in the car," he said.interact
This article originally appeared in The New York Times.