The Ca. State Board of Equalization's Pamphlet #59 ["California Local Motor Vehicle Fuel Taxation Law"] details how a gas tax could be put on a County-wide ballot. For Santa Clara County, a 3 cent per gallon gas tax would bring about $20M a year. (A $1.50 gas tax, in line with Europe's, would bring $1 Billion a year, but is not politically feasible). Guideway, bicycle, and/or pedestrian funding can be assured by specifying a percentage or dollar figure as part of the text placing it on the ballot.
The law states that these funds could be used for "streets and highways and their related public facilities for non motorized traffic." [Quote from CA Constitution Art. 19, which is cited by this law for use of funds.]. It also allows use for "guideways."
Information below is copied from the California State Board of Equalization, Pamphlet No. 59. To order, see bottom.
Article XIX of the California Constitution states in part that these fuel taxe revenues shall be used for "(a) ... highways (and their related public facilites for nonmotorized traffic), ... (b) exclusive public mass transit guideways ... and the maintenance of the structures ... for the public mass transit guideways ... "
Click on BOE-663 to download the order form (as .pdf file). Then order Pamphlet No. 59.