Once having entered a bicycle lane, no person riding or operating a bicycle shall leave such lane except at intersections; provided, that such person may leave a bicycle lane upon dismounting from a bicycle, walking the same, and being subject then to all laws applicable to pedestrians; provided further, that such person may leave the bicycle lane between intersections ill order to make a U-turn, where such a turn is permissible for vehicular traffic or to turn into driveways on the right or left hand sides of the bicycle lane. Upon leaving a bicycle lane, the rider or operator of such bicycle shall yield the right-of-way to all vehicles and shall not leave the bicycle lane until it is safe to do so. (Ord. No. 839, § 5.)