California Code, Public Utilities Code - PUC § 7612

It shall be unlawful for any owner or operator of a railroad running through or within the boundaries of the State of California and engaged in the business of common carrier to operate for or transport its employees in a rail track motor car which is not equipped with a transparent windshield sufficient in width and height to reasonably protect said employees, which said windshield shall be of plastic or safety glass and such car shall also be equipped with an electric headlamp of sufficient candle power as to render visible at a distance of 300 feet in advance of such car under ordinary atmospheric conditions, any obstruction, landmark, warning sign or grade crossing on such railroad, and said car shall also be equipped with at least one electric light on the rear end thereof with sufficient candle power as to be visible at a distance of 300 feet under ordinary atmospheric conditions, and such car shall also be equipped with a suitable device that will remove rain, snow and sleet from the windshield on such car. The head and rear lights provided for in this section shall only be required in the hours between one-half hour before sunset and one-half hour after sunrise.