infrastructure, in particular lead-times and access to the information needed to put it into place. (3) The Authority shall encourage infrastructure sharing between the operator concerning, in particular, posts, ducts and elevated points to be made available mutually on a commercial basis, where there is limited access to posts, ducts and elevated points resources through natural or structural obstacles. (4) The Authority shall(a) encourage access to alternative infrastructure on the basis of commercial negotiations, in order to foster and entrench competition as rapidly as possible; and (b) ensure that the access is provided under conditions of fairness, non-discrimination and equality of access. Number portability 55. (1) The Authority shall conduct market studies to assess consumers' portability needs and identify what categories of consumers are likely to request a portability service. (2) Where a need has been clearly identified, the regulations shall be made to allow consumers to keep their telephone numbers when they change operators. (3) The Authority shall(a) ensure that dialogue takes place between the market players and the Authority, and that the numbering plan is also revised so as to adapt it to the requirements of number portability; (b) establish tariff and technical conditions; and (c) provide information on national roaming contracts, in consultation with the market players. 75