51.  Network Rail must at all times afford reasonable facilities to the undertaker and its agents  for access to any works carried out by Network Rail under this Part of this Schedule during their  construction and must supply the undertaker with such information as it may reasonably require  with regard to such works or the method of constructing them.  52. —(1) If any permanent or temporary alterations or additions to railway property are  reasonably necessary in consequence of the construction of a specified work or a protective work,  or during a period of 24 months after the completion of that work in order to ensure the safety of  railway property or the continued safe operation of the railway of Network Rail, such alterations  and additions may be carried out by Network Rail and if Network Rail gives to the undertaker  reasonable notice of its intention to carry out such alterations or additions (which must be  specified in the notice), the undertaker must pay to Network Rail the reasonable cost of those  alterations or additions including, in respect of any such alterations and additions as are to be  permanent, a capitalised sum representing the increase of the costs which may be expected to be  reasonably incurred by Network Rail in maintaining, working and, when necessary, renewing any  such alterations or additions.  (2) If during the construction of a specified work or a protective work by the undertaker,  Network Rail gives notice to the undertaker that Network Rail desires itself to construct that part  of the specified work or the protective work which in the opinion of the engineer is endangering  the stability of railway property or the safe operation of traffic on the railways of Network Rail  then, if the undertaker decides that part of the specified work or protective work is to be  constructed, Network Rail must assume construction of that part of the specified work or the  protective work and the undertaker must, regardless of any such approval of a specified work or  the protective work under paragraph 48(2) pay to Network Rail all reasonable expenses to which  Network Rail may be put and compensation for any loss which it may suffer by reason of the  execution by Network Rail of that specified work or protective work.  (3) The engineer must, in respect of the capitalised sums referred to in this paragraph and  paragraph 53(a) provide such details of the formula by which those sums have been calculated as  the undertaker may reasonably require.  (4) If the cost of maintaining, working or renewing railway property is reduced in consequence  of any such alterations or additions a capitalised sum representing such saving must be set off  against any sum payable by the undertaker to Network Rail under this paragraph.  53.  The undertaker must repay to Network Rail all reasonable fees, costs, charges and expenses  reasonably incurred by Network Rail—  54. —(1) In this paragraph—  89 (e) in respect of any additional temporary lighting of railway property in the vicinity of the  specified works, being lighting made reasonably necessary by reason or in consequence  of the construction or failure of a specified work or a protective work.  (d) in respect of any special traffic works resulting from any speed restrictions which may in  the opinion of the engineer, require to be imposed by reason or in consequence of the  construction or failure of a specified work or a protective work or from the substitution or  diversion of services which may be reasonably necessary for the same reason; and  (c) in respect of the employment or procurement of the services of any inspectors, signallers,  watchkeepers and other persons whom it is reasonably necessary to appoint for  inspecting, signalling, watching and lighting railway property and for preventing, so far  as may be reasonably practicable, interference, obstruction, danger or accident arising  from the construction or failure of a specified work or a protective work;  (b) in respect of the approval by the engineer of plans submitted by the undertaker and the  supervision by the engineer of the construction of a specified work or a protective work;  (a) in constructing any part of a specified work on behalf of the undertaker as provided by  paragraph 48(4) or in constructing any protective works under the provisions of  paragraph 48(4) including, in respect of any permanent protective works, a capitalised  sum representing the cost of maintaining and renewing those works; 