Council may, by ordinance, provide for straightening or relocating any street previously opened which involves the opening of a portion of the straightened or relocated street over land not previously a portion of the street or the vacation of a portion of the previously opened street no longer to be used for street purposes. The straightening or relocation shall be considered as an opening or vacation and shall be effected in the same manner and by the same procedure as provided in section 1731 (relating to authority to open and vacate streets and procedure) but may be considered as a single proceeding to be effected by enactment of a single ordinance.