Section 17. Advertising for proposals

The board of transportation before
  awarding any contract except where there is an  extraordinary  emergency
  involving danger to life or property or where the estimated expense of a
  contract  does  not  exceed twenty-five thousand dollars shall advertise
  for proposals for such contract by a notice to be printed  once  a  week
  for  two  successive  weeks  in no less than two of the daily newspapers
  published in such city, and in such newspapers published elsewhere  than
  in  such city as such board shall determine. Such notice shall set forth
  and state the points within the city, between which such road is to run,
  the general method of construction, the route to be followed,  the  term
  of  years for which it is proposed to make such contract, and such other
  details and specifications as the board shall deem to  be  proper.  Such
  notice  shall  state  the time and place at which such proposals will be
  opened. The board shall attend at the time and place so  specified,  and
  shall publicly open all proposals that shall have been received, but the
  board  shall  not  be bound to accept any proposals so received, but may
  reject all such proposals and readvertise for proposals  in  the  manner
  provided in this chapter, or may accept any of such proposals as, in the
  judgment of such board, will best promote the public interest, and award
  a  contract  accordingly.  All  such  contracts must before execution be
  approved as to form by the corporation counsel and consented to  by  the
  board of estimate and the mayor of such city.