SAN FRANCISCO -- The BART strike that unleashed chaos on Bay Area highways Monday has become a business opportunity for ride-sharing and carpooling services and taxi-hailing apps, which have stepped in to help stranded commuters get to work.

Bay Area ride services Uber, Lyft and Sidecar jumped on social media networks over the weekend, as a strike began to look imminent, to recruit commuters who needed to get to work. Early Monday morning they filled the roads with their drivers, and the calls came in. By 9:30 a.m. Monday, Sidecar had seen a 40 percent increase in rides over the previous Monday, and had increased the number of drivers on the road by 50 percent to keep up with growing demand, said Margaret Ryan, vice president of communications.

Public transit strikes are a marketing opportunity for these ride-sharing companies. Uber, which uses an app to dispatch black town cars, taxis and low-cost rides in hybrids or small cars, said it planned to visit some BART stations during the strike to recruit commuters without a ride. The company offered free rides in Boston when one of the city's mostly highly used rail lines shut down for several weekends in late 2011 and early 2012.

The three startups said the strike proves that the congested Bay Area needs more transportation options, and ride-sharing services will help to mitigate the economic blow of the strike by helping commuters get to work and keep businesses open.

"In times of crisis, this is when alternative transportation services like Sidecar are at their best," Rachael King, national social media manager for Sidecar, wrote in a blog post on the company website.

Despite their growing popularity among commuters, ride-sharing and car service apps continue their battle with state and local regulators, who say the companies violate public safety rules and should be licensed like city taxi cabs. The state Public Utilities Commission last year fined Uber, Sidecar and Lyft's parent company, Zimride, and last month the Los Angeles Department of Transportation sent the three companies a cease and desist order, which the companies rejected.

Sidecar, which makes money by taking a cut of the fees that riders pay to drivers, is letting all drivers keep those fees between 6 a.m. and 7 p.m. on weekdays.

Companies with taxi-hailing apps are also cashing in. Flywheel, an app that lets riders hail and pay for taxis on their smartphone, expected to see a surge in demand from riders who typically take BART from outlying neighborhoods in San Francisco to the city center, said Brogan Keane, chief marketing officer. The company, based in Redwood City, works with about 900 cabs in the Bay Area and makes about 60 cents off each passenger those cabs pick up using the Flywheel app.

Commuters board an AC Transit bus on July 1, 2013 in Oakland, California. (Photo by Justin Sullivan/Getty Images)
Commuters board an AC Transit bus on July 1, 2013 in Oakland, California. (Photo by Justin Sullivan/Getty Images) (Justin Sullivan)

Demand for taxi-hailing app Taxi Magic was "very heavy, but not insane" Monday morning, said Matt Carrington, marketing director for the company, which serves San Francisco and San Jose. If the afternoon commute picks up, Taxi Magic will roll out a premium service that requires passengers to pay $5 or $10 more but guarantees that the cab would show up when called to a home or business, Carrington said.

"When there is a lot of demand out there, especially on the street, (cabs) will pick up the street hail and they're not as likely to go pick up someone five miles down the road," he said.

Some San Francisco residents said they had to take a cab to work because the buses, which are operated by the San Francisco Municipal Transportation Agency, or Muni, were too full to stop at all bus stops.

Other commuters turned to carpooling as a cheaper alternative. Avego, a website and smartphone app that helps Bay Area commuters set up carpools, added about 700 drivers between midnight and 7 a.m. Monday, said CEO Sean O'Sullivan. Those drivers picked up commuters who work nearby, lessening the number of cars on the road, although it may not have been noticeable Monday. In some places, a 40-minute commute grew to two hours.

"Today was a horrific day for drivers," O'Sullivan said. "It's been hellacious."

The crawling commute home won't be agonizing just for drivers, it could also snarl reservations at car rental sites during the peak of summer vacation travel. Employees at the Avis and Budget rental sites in San Francisco's Soma neighborhood said they were worried that heavy traffic would delay car returns. That would mean cars may not be ready for customers with reservations Monday evening or Tuesday morning who are trying to get away for the Fourth of July weekend.

Contact Heather Somerville at 925-977-8418. Follow her at Twitter.com/heathersomervil.