While the Facebook funding will be used to study ways to improve the commute over the current Dumbarton Bridge, planners will also look at creating a bicycle/pedestrian trail or express bus service on the old span, Bartholomew said in an interview.
"Maybe we're not necessarily providing passenger rail service, but maybe we can use that path to provide some sort of bike-pedestrian trail or we look at bus rapid transit along that area."
SamTrans wants to explore ways to improve bus service over the existing Dumbarton and make it easier for drivers to get to the bridge from nearby roads.
Weekday morning traffic on the bridge has grown 27 percent since 2010. SamTrans' Bartholomew lives on the Alameda County side of the bridge and is one of the thousands who suffers through that commute.
"When I do have to drive over, you can definitely see the shift that's happened getting across the bridge, whether it's the Dumbarton or the San Mateo Bridge," said Bartholomew. "They're much more crowded than they used to be."
One critic of Bay Area transit planning says Facebook's funding of the study raises serious concerns about who is setting the agenda for a crucial public service.
"Kudos to Facebook for stepping up, but this is an awfully bad precedent," Jason Henderson, a San Francisco State professor specializing in transportation, said in an email.
Henderson said local transit leaders have neglected future planning for the Dumbarton corridor.
"The end result: a large corporation donating money to study a much needed regional rail and bus connection," Henderson said. "That is a sad commentary on the sorry state of regional planning in the Bay Area. It raises long-term questions of accountability -- who does the study? Is it just to benefit Facebook or the region?"
Facebook, whose employees are bound to benefit from transit improvements, says the money could help solve a shared local problem.
"Facebook is committed to supporting initiatives that help reduce regional roadway congestion and is pleased to partner with SamTrans to explore ways of improving traffic and transit options on the Dumbarton corridor," said the company's campus facilities director, Fergus O'Shea, in a joint statement with the transit district.