As Olivia Cho began to plan her winter break travels, she logged in to her James Madison University Zimride account to find a cheap and safe ride home.

She found a few rides being offered to Northern Virginia, so she looked up the profiles of the drivers through her school’s Zimride social network and then sent e-mails to them. Cho eventually traveled from the Shenandoah Valley to McLean with other JMU students. She didn’t know any of them, but in the days leading to the trip, they got to know one another online.

“At first, I was a little apprehensive,” said Cho, 19. “The very first drive is kind of odd because you don’t know who the person you are riding with is. But it is usually not bad.”

Zimride, a San Francisco-based company, is growing popular on college campuses, including eight universities in the District, Maryland and Virginia. The service allows users to find and post rides through its university networks. The driver sets the fee; usually, the passenger pays Zimride, and Zimride pays the driver, eliminating the often uncomfortable situation of exchanging cash.

Cho has used Zimride for a few months, mostly to travel between home and school. And so far, she said, it works fine for her needs.

“It is also a lot cheaper than taking the bus when the ticket for the bus is about $40, and when you catch a ride with somebody you really only pay anywhere between $10 and $15,” said Cho, a sophomore.

The service is integrated with Facebook, which “helps provide people with more information about who they will ride-share with, so they can establish a level of trust,” Zimride co-founder John Zimmer said.

Zimride, which Zimmer launched in 2007 with co-founder Logan Green, has more than 300,000 users nationwide and 120 networks for universities and companies. The number of users has doubled in the past year, Zimmer said. On its Zimride network, the company is promoting routes for the public, such as San Francisco to Lake Tahoe, on the weekends.

In the Washington region, universities are promoting Zimride as a commuter alternative for staff members and students. At this time of year, they encourage students to use the Zimride social network to find rides to holiday destinations.

Online matching services for ride-sharing, such as Zimride, are not new. Since the 1970s, the Metropolitan Washington Council of Governments has offered Commuter Connections, a regional network that became one of the first in the country to offer computerized carpool-matching. But Zimride’s social networking feature has been a highlight for university communities.

Some experts say carpooling services are particularly valuable in the Washington region, home to the worst traffic congestion in the nation, with commuters spending an average of 74 hours stuck in traffic each year.

“One of the greatest waste in resources in America are those extra seats in those cars that are traveling every day,” said Alan Pisarski, a transportation expert and author of “Commuting in America.” “The opportunities to fill those seats in various ways is immensely valuable.”

Zimride users rely on the service for occasional car-sharing and to build a network of people with similar commutes.

“You just connect with people through your cellphone and make that arrangement in a more personal way,” said Pisarski, who calls the service a modern extension of hitchhiking and carpooling.

At the University of Maryland, where there is a significant off-campus population, about 4,000 students and staff members have signed up to use Zimride.

The university has encouraged the use of the ride-sharing service through contests and incentives, offering students who carpool reduced parking fees and preferred parking, said Beverly Malone, a spokeswoman for the University of Maryland Department of Transportation Services.

“Our traffic is terrible during class change. . . . We needed to look for strategies, and this is one,” Malone said.

At George Mason University — with 33,000 students and 6,000 staff members — officials say they hope to reduce the number of cars on campus by increasing the number of people carpooling.

It is “a 21st-century ride-sharing board,” said Josh Cantor, director of parking and transportation at George Mason. “In the early ’90s, it was common in the student centers to have a tag board where you would say ‘I am looking for a ride to New York City for the weekend.’ This is kind of the modern electronic version of that.”