Gov. Jerry Brown on Monday signed a bill allowing Alameda County voters to consider a tax hike to help fund transportation projects.

Assembly Bill 1086 gives the Alameda County Transportation Commission the right to place the tax increase on the November 2012 ballot. State law had previously prohibited the ballot measure because a tax hike would have raised rates in San Leandro and Union City, which have their own sales taxes, above legal limits.

Commissioners have not yet decided whether to ask voters to extend the current half-cent countywide sales tax or to raise the tax to a penny. Either action would need to be approved by two-thirds of the voters.

The one-time exemption was requested by Assemblyman Bob Wieckowski, D-Fremont. The commission is expected later this year to release a draft of the plan on how it would spend the tax money.