It shall be the general duty of a Corporation so to exercise its powers as progressively to provide or secure or promote the provision of, an efficient, adequate, economical and properly co-ordinated system of road transport services in the ¹[Union territory of Delhi or part thereof] for which it is established and in any extended area:
     Provided that nothing in this section shall be construed as imposing on a Corporation, either directly or indirectly, any form of duty or liability enforceable by proceedings before any Court or Tribunal to which it would not otherwise be subject.