No freight car shall be allowed to stand on any spur track during the hours of darkness in any part of any public street, either singly or at the end of a number of connected cars, facing any oncoming traffic which may use or approach such street, unless at all such times such car is equipped with one or more red reflectors on the end thereof facing such traffic or suitable illuminating devices are so placed in the vicinity that they will delineate the extent of the obstruction.