California Code, Public Utilities Code - PUC § 99564

An employee organization may become the exclusive representative for the employees of an appropriate unit for purposes of meeting and conferring by filing a request with a transit district employer alleging that a majority of the employees in an appropriate unit wish to be represented by the organization and asking the employer to recognize it as the exclusive representative. The request shall describe the grouping of jobs or positions that constitute the unit claimed to be appropriate and shall certify that proof of majority support has been submitted to either the board or to a mutually agreed upon third party. Notice of any such request shall immediately be posted conspicuously on all employee bulletin boards in each facility of the employer in which members of the unit claimed to be appropriate are employed.