Section 61. Farm and road bridges

The commissioner of transportation is
  authorized and required to maintain until April first, nineteen  hundred
  fifty-four,  at  public  expense  farm, road and street bridges over the
  canal system, in all places where such bridges were constructed prior to
  the twentieth day of April, eighteen hundred  thirty-nine,  if,  in  his
  opinion,  the public convenience requires that they should be continued,
  whether heretofore maintained at the expense of  the  state  or  of  the
  counties,  towns,  villages and cities where they are situate, provided,
  however, that commencing on the first day  of  April,  nineteen  hundred
  fifty-four,   and   continuing   thereafter,  the  maintenance,  repair,
  improvement, replacement or closing of any such bridge over any  section
  of  the  canal  heretofore abandoned or which may hereafter be abandoned
  shall be governed by the provisions of the highway law, except that  any
  such  bridges situate in a city shall be maintained, repaired, improved,
  replaced or closed in the same manner and subject to the same provisions
  of law as apply to other streets and bridges in such city.