Whenever any portion of the Interstate System that is to be constructed within cities or towns is to occupy existing streets, the right-of-way in the street shall be occupied by the Interstate System free of cost to the Commonwealth. When the Interstate System extending into or through cities or towns has been constructed to the required standards, streets or highways occupied thereby shall cease to be maintained and controlled by the governing bodies of such cities or towns, and such cities and towns shall thereafter be relieved from all civil liability arising from the physical condition of such streets or highways. Such streets and highways shall not be considered as mileage for which the Board is required to make payment to such cities or towns by any other provision of law. Nothing contained in this article shall relieve the cities or towns through which any portion of the Interstate System is projected from the responsibility for the preservation of public peace, prevention of crime, apprehension of criminals, protection of the rights of persons and property, and enforcement of the laws of the Commonwealth, and the regulations enacted pursuant thereto, nor shall anything contained herein be considered as a waiver by the Commonwealth of its immunity from liability for tort.