Union members rejected the agreement by a vote of 944 to 488 on Wednesday.
The agreement came after three months of negotiations between Muni and the Transport Workers Union Local 250-A and would have saved the agency a minimum of $38 in labor costs over the three-year contract.
Muni officials said that they expect a decision by the arbitrator by next Tuesday, the latest date the proposed contract could be submitted in compliance with sunshine laws.
The new contract will take effect on July 1, the beginning of the fiscal year.
Photo Credit: Lensovet, via Wikimedia Commons