A free shuttle from San Rafael’s downtown transit center to the Larkspur Ferry Terminal is expected to start in September as a nine-month pilot project.

The Golden Gate Bridge District’s Transportation Committee and full board has approved the plan.

“There are a lot of options to get to the San Rafael Transit Center: bikes, buses and there is the park-and-ride lot under the freeway,” said Golden Gate Planning Director Ron Downing. “There are a lot ways to get to the center and we think people will then use the shuttle to get to the ferry.”

The shuttle will likely be known as Route 21 and might be expanded west beyond downtown, but details on how that might work are still being developed, Downing said. The ferry shuttle would join Route 25 out of the Ross Valley and Route 37 from Terra Linda and Lucas Valley, which deliver commuters to boats in Larkspur.

Golden Gate transit officials looked at linking Route 37 to downtown San Rafael, but quickly determined that morning and evening traffic along Highway 101 was too heavy and would serve to delay shuttle service to a point where it would be unattractive to riders, Downing said.

“In the morning it is backed up getting into San Rafael, in the afternoon it is backed up with all the traffic coming off of 580,” Downing said. “It would delay trips back to Lucas Valley and Terra Linda by at least 10 minutes.”

So the new Route 21 will run direct from San Rafael to the ferry terminal.

“A lot of transit comes together there, so it seems like a logical place to try a shuttle,” said Denis Mulligan, bridge district general manager.

Similar to the current schedule for the other shuttles, the buses would meet morning ferry departures from Larkspur to San Francisco between 7 a.m. and 10:10 a.m. The shuttles would pick up passengers from ferries arriving between 4 p.m. and 7 p.m. The shuttles would be dedicated for ferry riders and not intermingle with other bus commute service.

The service is not expected to attract a large number of new riders to the ferry, but rather take drivers off the road who would otherwise drive to the ferry terminal. If the route proves successful it has the potential to scoop up riders at the Larkspur SMART train station and take them to the ferry terminal. SMART service to Larkspur is expected to be established after San Rafael to Santa Rosa train service begins in 2016.

The new shuttle service will cost $265,000 to operate during the pilot period, with $261,000 coming from state grants from the Low Carbon Transit Operations Program under the state’s Cap and Trade Program. The district will contribute $4,000.

“Customers have been clamoring for this new shuttle so they can easily get to the ferry from downtown San Rafael and vice-versa,” said Priya Clemens, district spokeswoman. “It’s one more option we’re providing so people can easily travel in the North Bay while leaving behind their cars and congested parking lots.”