(1) Where the proof of the commission of an offence under this Part of this Act involves the proof of the speed at which a person (whether the accused or another person) was driving a vehicle on a particular occasion, the uncorroborated evidence of one witness stating his opinion of the speed at which such person was driving such vehicle on that occasion shall not be accepted as proof of such speed.
(2) Where a person is charged with an offence under this Part of this Act and the act constituting such offence consists of driving a vehicle in contravention of a provision of this Part of this Act, such person shall not be convicted of such offence unless or until the court is satisfied either -
(a) that such person was warned at the time of the commission of the offence or immediately thereafter that he would be prosecuted therefor, or
(b) that within such time, not exceeding fourteen days, after the commission of the offence as the court shall consider to have been reasonable, noti