As their colleagues circled the block, dozens of taxi drivers gathered on the steps of City Hall to call for the regulation of rideshare companies such as Lyft, Sidecar and Uber.
One of the rally's organizers, Barry Korengold, president of the San Francisco Cab Drivers Association, called the startup companies "unfair competition."
He said, "legal cabs are getting screwed," citing a large drop in taxi ridership since the companies began operating.
The taxi drivers are asking city officials and the California Public Utilities Commission to step in.
The CPUC, which regulates passenger carriers, has asked an administrative law judge to compile a report on rideshare companies.
In December, the commission tasked the judge with gathering information to "evaluate the safety of ridesharing businesses that utilize the Internet, social media, and location services to arrange transportation of passengers over public highways for compensation," according to CPUC documents.
That report is expected to be released sometime this week, and then will be open to public comment for 30 days before the commission votes on any of the judge's recommendations.
Mark Gruberg, head of United Taxicab Workers, called for the CPUC "to put an end to these unlawful companies."
"Come on, San Francisco," he said. "Respect and enforce the law."
Taxi drivers said they take issue with the term "rideshare" being applied to such companies. As defined by the CPUC, a rideshare involves a driver transporting passengers to a destination, usually work-related, without profiting from the ride.
Korengold said it is untrue that the drivers and companies don't profit from the interaction.
"Let's all play by the same rules," he said.
Some protesters cited discrimination, with rideshare companies largely unable to pick up disabled and handicap passengers.
Taxi driver Ruah Graffis, sitting in a motorized wheelchair, said, "We'd like to support the real cab drivers of the city who pick up everybody."
Another driver, Jeffrey Rosen, said taxi drivers are trained, regulated, and constantly inspected, all in the name of public safety. He called the ride services offer "rogue, bandit taxis with a smartphone and a Facebook account."
Many protesters held signs bearing a photo of Mayor Ed Lee sporting a pink mustache, similar to those placed on the front of Lyft vehicles.
Other signs read "Stop taxi deregulation" and "Real drivers do it with insurance."
After the noon City Hall rally, the long line of taxis headed to the CPUC building at McAllister Street and Van Ness Avenue to continue the protest there.