A proposed power shift that would give Oakland and San Jose each an extra vote on the Bay Area's powerful regional transportation commission is headed for a key vote Wednesday amid reservations by Contra Costa County members.

The Metropolitan Transportation Commission -- a nine-county transportation funding and planning body -- will consider whether to seek state legislation expanding its panel from 16 to 18 voting members so that Oakland and San Jose mayors can each pick a representative.

Representatives from Alameda and Santa Clara counties contend the two big cities deserve a larger voice because they will shoulder the biggest share of the Bay Area's responsibility for planning transit-friendly residential and business developments to meet state mandates for reducing greenhouse gas emissions.

"To ask the city to take on that burden and not give it a voice in those decisions is inherently unfair," said Ken Yeager, a Santa Clara County supervisor and former San Jose councilman who serves on the nine-county transportation commission.

The commission holds the purse strings over millions of dollars a year in state and federal transportation funds allocated in the Bay Area.

San Francisco is the only city to directly pick an MTC commissioner. Other members are picked by county boards of supervisors or mayors' associations, except for two picked by regional planning agencies. The commission also includes three nonvoting members.

The proposed change would mean that Alameda and Santa Clara counties would be guaranteed at least three commissioners from within their borders while other counties would have either one or two commissioners.

In defense of that shift, Yeager and Alameda County Supervisor Scott Haggerty, the MTC chairman, said their counties are the two biggest -- with 1,582,420 in Alameda County and 1,890,909 people in Santa Clara County.

Two MTC members from Contra Costa County -- County Supervisor Federal Glover and Orinda Councilwoman Amy Worth -- said they are not convinced the two cities deserve the extra votes on a panel that relies on regional cooperation.

"Why do they need the extra votes if we're all in this together?" Worth said. "It's a question to be discussed."

Glover said Contra Costa County's population has grown by as many people as Alameda County's in the past four decades even though Contra Costa's total population of 1,079,160 is smaller.

The commission meets 9:30 a.m. Wednesday at the MetroCenter, 101 Eighth St., Oakland.

Contact Denis Cuff at 925-943-8267. Read the Capricious Commuter at IBABuzz.com/transportation. Follow him at Twitter.com/deniscuff.