It's part of a protest against BART's plans to link its Coliseum Station to the Oakland Airport with a light-rail system.
The group Transform claims in a recent report that each trip on the line will cost taxpayers $102 for the first 35 years that the connector is in operation.
Organizers of today's demonstration claim buses can move passengers to and from the airport faster than BART's proposed rail link.
BART expects the system to cost nearly $500 million.
