Whenever in the judgment of the board or body having control of the streets of any city of the first or second class, public interest or convenience requires an extension therein of street railway tracks to connect or make a detour of existing tracks, such board or body may:

a. After notice and hearing in the manner prescribed by law in the case of application for consent to construct street railways in the streets thereof, by ordinance authorize the construction, maintenance and operation of the extension for either of the purposes aforesaid.

b. In the event of the failure of the street railway or traction company or companies operating the street railway line or lines proposed to be connected by the extension authorized in paragraph “a” of this section, after opportunity for a hearing before said board or body has been given to the street railway or traction company or companies, by ordinance require the construction, maintenance and operation of the extension for either of the purposes aforesaid.

No one extension constructed pursuant to this section shall exceed one-half mile in length nor shall any authority or requirement to operate the extension be for a longer term than fifty years.

For such extension it shall not be necessary to obtain the consent of any of the owners of the land fronting on the line thereof.

No privilege granted, or requirement made, by or under the authority of this section, shall be valid or effective until approved, after hearing, by order in writing by the board of public utility commissioners.