Cal. Labor Code § 6901

(a) No common carrier operating more than four trains each way per day of 24 hours on any main track or branch line of railroad within this state, or on any part of a main track or branch line, shall run or permit to be run, on any part of a main track or branch line, any passenger, mail, or express train on which there is not employed at least one conductor, one brakeman, and the following: (1) One engineer and one fireman for each diesel locomotive. (2) One electric motorman for each train propelled or run by electricity. (3) One motor or power control man for each train propelled by motive power other than diesel or electricity. (4) Two brakemen, where four or more cars, exclusive of railroad officers’ private cars, are hauled. (5) One baggageman, except on a train upon which baggage is not hauled, and on gasoline motorcars. (b) This section does not apply to any diesel locomotive weighing 45 tons or less. (c) Paragraph (4) of subdivision (a) does not apply where its application would conflict with the terms of a collective bargaining agreement. (d) Subdivision (a) does not apply to the San Diego Metropolitan Transit Development Board or the North San Diego County Transit Development Board. (e) With respect to commuter train service provided by the San Diego Metropolitan Transit Development Board or the North San Diego County Transit Development Board, there shall be at least one qualified crewmember inside a train car set during revenue service. For the purpose of this subdivision, “revenue service” means service during which passengers are carried or are scheduled to be carried.