Competing ferries. If the commission shall provide for the issuance hereunder of a single issue of revenue bonds for the purpose of paying the cost of constructing a bridge or tunnel and of acquiring a ferry or ferries within 5 miles of the location which shall be selected for such bridge or tunnel, the commission shall not be required to maintain or operate any such ferry but in the discretion of the commission any such ferry, with the appurtenances and property thereto connected and belonging, may be sold or otherwise disposed of or may be abandoned and dismantled whenever in the judgment of the commission it may seem expedient so to do. The proceeds of any sale or disposition of any ferry or ferries shall be paid into the sinking fund hereinabove provided for the bonds.