The driver of a vehicle overtaking upon the right any streetcar stopped or about to stop for the purpose of receiving or discharging any passenger shall stop the vehicle at least five feet (5') to the rear of the nearest running board or door of the streetcar and thereupon remain standing until all passengers have boarded the car or, upon alighting, have reached a place of safety. However, where a safety zone has been established, a vehicle need not be brought to a stop before passing any streetcar but may proceed past such car at a speed not greater than is reasonable and proper and with due caution for the safety of pedestrians.