6. (1) No person shall, while he holds any driving licence for the time being in force, hold any other driving licence except a driving licence issued in accordance with the provisions of section 15, or a document authorising, in accordance with the rules made under section 107, the person specified therein to drive a motor vehicle. (2) No holder of a driving licence shall permit it to be used by any other person. (3) Nothing in this section shall prevent a licensing authority having the jurisdiction referred to in sub section (1) of section 7 from granting a professional or a non professional driving licence if the person is found fit for the said driving licence or from adding to the classes of vehicles which the driving licence authorises the holder to drive.