All carriers affected by this Act shall initiate the training program within 1 year of the effective date of this Act in the following manner:
     (a) all persons who are presently operating employees are to receive training within 3 years.
     (b) beginning 2 years after the effective date of this Act, all employees newly assigned to operative duties are to receive training within 4 months following of their assignment.
     (c) all employees newly assigned to operative duties between 1 and 2 years after the effective date of this Act are to receive this training within 3 years.
     (d) Beginning 3 years after the effective date of this Act, all operative employees are to receive refresher courses at least once every 2 years.