Section 31. Municipal construction of railroads

It shall be the duty of
  the  board  of  transportation  to  consider  the  routes,   plans   and
  specifications, if any, previously laid out and adopted by them or their
  predecessors,  and for which the consents have been obtained referred to
  in section twenty-one of this chapter; and either to  proceed  with  the
  construction of such railroad, and provide for the operation thereof, or
  to  change  and  modify  such  routes,  plans  or specifications in such
  particulars as to such board may seem to be desirable, or from  time  to
  time  and  with  or without reference to former routes or plans to adopt
  other or different or additional routes, plans  and  specifications  for
  such  railroad.  In  all  cases in which any such change or modification
  shall be of such character as to require the consents  thereto  referred
  to in section twenty-one of this chapter and in all cases where other or
  different routes or general plans may have been so adopted, the board of
  transportation  shall  proceed  to  secure  the  consents required to be
  obtained by section twenty-one of this chapter. Prior to the time of the
  final grant of any franchise under the provisions of this chapter or the
  making of  a  contract  for  construction  of  any  railroad  under  the
  provisions of this chapter, the board of transportation shall have power
  to  rescind  and revoke any resolution of such board or its predecessors
  adopting any routes or general plan for a railroad adopted by such board
  or its predecessors and, in  the  discretion  of  such  board,  in  lieu
  thereof  to  adopt new routes and a general plan. Every such rescindment
  or revocation which shall have been made by such board of transportation
  or its predecessors shall be deemed to have been lawful  and  authorized
  by  the rapid transit act, as the same was in effect on the twenty-third
  day of April, nineteen hundred.
    b. As soon as such consents, where necessary, shall have been obtained
  for any railroad and the detailed plans  and  specifications  have  been
  prepared  as  provided in section twenty-two of this chapter, such board
  of transportation, for and in behalf of such  city,  may  enter  into  a
  contract  with  any  person, which in the opinion of such board shall be
  best  qualified  to  fulfill  and  carry  out  such  contract  for   the
  construction of such road, including such sub-surface structures as such
  board  may  include  in  the  plans for such road under the authority of
  section twenty-two of this chapter, upon the routes  and  in  accordance
  with  the plans and specifications so adopted, for such sum of money, to
  be raised and paid out of the treasury of such city, as provided by this
  chapter, or to be contributed in part or in whole for  the  construction
  of such road by the contractor having the contract for the equipment and
  operation  of  such  road  as  a  consideration  for  the making of such
  contract for equipment and operation as provided by this  chapter.  Such
  contract  for  construction shall contain such terms and conditions, not
  inconsistent with the aforesaid plans and specifications, as such  board
  shall  determine  to be best for the public interests.  The sum of money
  to be paid for the construction of such road shall be separately  stated
  in  the contract from the sum to be paid for any sub-surface structures,
  the construction of which is provided for in such contract. Such  board,
  in any case, may contract for the construction of the whole road, or all
  the  roads  provided  for  by  such  plans  in a single contract, or, by
  separate contracts, executed from time to time, or  at  the  same  time,
  with  one  or  more  such persons, may provide for the construction of a
  part of such road or for the construction at first of two or more tracks
  over a part of such road and afterwards of one or more additional tracks
  over a part of such road  as  the  necessities  of  such  city  and  the
  increase   of   its   population  or  the  advantageous  and  economical
  performance of the work in the judgment of such board  may  require.  In
  the  alternative  such  board,  in  its discretion by separate contracts

  executed from time to time or at the same time, may contract with one or
  more persons for the performance of any kind of work or any  portion  of
  the work or for the furnishing of any material or for the performance of
  any  labor necessary for or incidental to the construction of such road.
  In any case where any such contract which shall have been  entered  into
  provides  that  upon  the happening of any event or default specified in
  such contract such board shall have the right and be  entitled  to  take
  over  and  perform  or  complete  or  contract  for  the  performance or
  completion of the work embraced in such contract or  any  part  of  such
  work,  such  board,  upon  the happening of any such event or default so
  specified in such contract, with the approval of the board  of  estimate
  and  the  mayor,  also may employ such persons and purchase or hire such
  plant, tools, machinery, supplies and materials as may be necessary, and
  itself perform or complete the work embraced in  such  contract  or  any
  part of such work as in its judgment the public interests require.
    c. The board of transportation, in the contract for a part of any such
  railroad,  also  may  insert a provision that at a future time, upon the
  requirement of the board, the contractor shall construct  the  remainder
  or  any  part of the remainder of such road, as the growth of population
  or the interests of the city, in the judgment of the board, may require.
  Such board may insert in such contract provision for a method for fixing
  and ascertaining at such future time  the  amount  to  be  paid  to  the
  contractor  for  such  additional  construction,  and to the end of such
  ascertainment may provide for arbitration or for determination by  court
  of  the  amount  of  such  compensation,  or  of  any  other  details of
  construction which shall not be prescribed in the  contract,  but  which
  shall  be  deemed  necessary  or convenient by such board. If the public
  interest, in the opinion of the board, shall justify the provision,  any
  such  contract  may  provide  that  the  construction  of any section or
  portion of the railroad included in such contract, with the  consent  of
  such  board,  may  be  suspended  during  the  term  of operation of the
  railroad as provided in this section, or any part of such  term.  During
  such  term  or part of term there shall be available for use, in lieu of
  such portion of the road, a railroad or a portion  or  section  thereof,
  which,  with  the railroad or portion of railroad constructed under such
  contract, shall form a continuous and convenient route.
    d. Any such contract may be made for the construction of such road  in
  sections,  or  for  the  construction  of any section thereof. Except as
  otherwise provided in this chapter, every such  contract  shall  specify
  when  the  construction  of the railroad or the section thereof included
  therein shall be commenced in each case, and, in each case, the date  of
  completion.  The  board  of  transportation  may  by  any  such contract
  determine when and how the work of construction of the railroad included
  therein shall proceed. The board may also provide for the  equipment  at
  public  expense  of  such  railroad  in connection with the construction
  thereof, and may include in any contract for construction authorized  by
  this  chapter  provision for the equipment, or any part thereof, of such
  railroad, but may make a separate contract for the whole or any part  of
  such equipment with the constructing contractor or any other responsible
  persons.  Any  such  contract,  in  lieu  of requiring the contractor to
  provide equipment or any part thereof for generation  or  furnishing  of
  motive  power,  may authorize the contractor to enter into a subcontract
  for purchase and delivery as required of motive power for  operation  of
  such railroad, provided such subcontract, as to the parties thereto, the
  sureties  thereon  and the terms thereof, shall be first approved by the
  board.  In  the  alternative  such  contract  may   provide   that   the
  construction  or  completion  of  equipment, or any portion thereof, for
  generation or furnishing of motive power included in such contract, with

  the consent of the board, may be suspended during a  period  designated,
  provided  that  during such period there shall be available for use when
  required, in lieu of such  equipment,  motive  power  furnished  to  the
  contractor  under  and  pursuant  to  the  terms  of  a contract for the
  purchase of power, which contract shall, as to the parties thereto,  the
  sureties  thereon and the terms thereof, be first approved by the board.
  In case of the expiration or termination, of the contract for equipment,
  maintenance and operation of such road, as provided in this chapter, any
  subcontract for the furnishing of power may be terminated or taken  over
  by  the  city  without  making any allowance or paying any amount to the
  contractor for or on account of any unexpired term of such subcontract.
    e. Any railroad constructed by and at the expense of the city shall be
  and remain the absolute property of the city, and shall be and be deemed
  to be a part of the public streets of the city, to be used  and  enjoyed
  by the public subject to such reasonable rules and regulations as may be
  imposed and provided for by the board of transportation.