Carpoolers currently pay no toll during rush hour.
The full board will consider the item Friday. The board will hold a public hearing May 14 and vote on the toll increases May 28.
The carpool toll, expected to raise $1.3 million in fiscal year 2010-11, would take effect July 1. Only 2.3 percent of the 19 million southbound bridge crossings in fiscal year 2008-09 were carpools, according to the bridge district.
Tolls for multi-axle vehicles will generally double. The toll for vehicles with three or more axles using Fastrak would be $5 per axle with a maximum toll of $35. Those paying cash would be charged $6 per axle with a maximum of $42.
Those increases would be phased in over the next two years and would raise an additional $600,000 in fiscal year 2010-11 and $1.2 million in fiscal year 2012-2013.
In fiscal year 2008-09, less than 1 percent of the 19 million vehicles making the southbound crossing were vehicles with three or more axles, according to the district.
The district's auditor-controller Joseph Wire told the Finance-Auditing Committee that state bridges in the Bay Area also are charging carpoolers half the cash toll starting July 1 and are also increasing tolls on multi-axle vehicles.
The district's general manager, Celia Kupersmith, said most carpoolers are from Sonoma County and northern Marin County.
Carpool vehicles on the Golden Gate Bridge are defined as two-axle vehicles with three or more passengers. Motorcycles and buses also qualify. Such vehicles are not charged a toll from 5 a.m. to 9 a.m. and 4 p.m. to 6 p.m. on weekdays.
Clean-air vehicles with white California DMV Clean Air decals, which also cross toll-free during commute hours, would also have pay the $3 toll under the proposal.
Cars with yellow California DMV Clean Air decals do not currently receive a carpool discount and will continue to be treated as regular vehicles and pay $6, District spokeswoman Mary Currie Currie said.
Carpool vehicles would be required to use FasTrak to pay the $3 toll, Currie said. Carpools would still have to stop in a staffed lane at the toll plaza for manual verification.
District staff members are concerned that without an increase, drivers of multi-axle vehicles would take the Golden Gate Bridge to avoid the higher tolls on state-owned bridges, Currie said.
That could lead to increased congestion on the bridge, which would be particularly troublesome during the reconstruction of Doyle Drive, Currie said.
There will be an informational open house on the proposed toll hikes April 7 in San Rafael.
The proposed toll increases were among 33 initiatives discussed in October for addressing a projected five-year, $132 million budget shortfall, Currie said.