Any vehicle attempting to reenter traffic while parked at the curb shall yield the right of way to oncoming traffic in the street approaching from the rear. The parked vehicle shall proceed into the line of traffic only after the driver has given the appropriate signal which indicates his intention of turning from the curb and into the line of traffic. The vehicle shall in no event enter the line of traffic until the driver has ascertained that no hazard exists. (Prior code ch. 20)