53 Pa. Stat. § 1835
When a municipality intervenes between two ends of a county highway, and the municipality has failed to properly improve the municipal streets or highways constituting the shortest and most reasonable route through said municipality, which will connect the two ends of such highway, it shall be lawful for the councils of such municipality to authorize, by ordinance, that the proper corporate authorities of the municipality contract, in the manner herein provided, with the county commissioners, that the shortest and most reasonable route through said municipality connecting the two ends of such highway be improved.
Or, when a county highway terminates at the corporate limits of a municipality in the same or in another county, and connects with a municipal street or alley which the municipality has failed to properly improve, and the county commissioners of the county in which the municipality is located deem the improvement of such municipal street or alley necessary, in order to make such county highway easily accessible to the residents of the municipality or to the traveling public, it shall be lawful for the councils of such municipality to authorize, by ordinance, that the proper corporate officials of the municipality contract with the county commissioners, in the manner herein provided, that such municipal street or alley, or any part thereof, be improved; and also that there be improved, when necessary, any part or parts of the streets connected therewith which connect the said county highway with the business district or districts of said municipality, or with a system of improved streets therein, or which connect the said highway with another county highway terminating at the limits of said municipality. If several municipalities are contiguous to each other, and at the corporate limits of any one of them a county highway terminates, and one or more of such municipalities have failed to properly improve any municipal street or alley therein, and the county commissioners deem the improvement of such street or alley necessary, in order to make such highway easily accessible to the residents of the municipality or to the traveling public, it shall be lawful for the councils of such municipality or municipalities to authorize the proper corporate authorities to enter into a similar contract with the county commissioners. The county commissioners shall have the power to improve said streets or alleys as herein provided, and said powers herein given shall also include the right to widen, repave, or otherwise improve said municipal streets and alleys, whenever the same is necessary to accomplish the purpose herein conferred. Whenever an improvement is made to a municipal street or alley pursuant to this section, it shall be lawful for the county to pay the total cost of such improvement, or the cost may be divided between the municipality and county. The municipal ordinance authorizing the improvement shall stipulate what percentage of the cost, if any, shall be borne by the municipality, and what percentage of the cost shall be borne by the county. The contract for any such improvement may be taken by the county, upon the stipulation by the municipality to pay its proportionate share of the cost, if any, upon the completion of the work; or it may be taken by the municipality, upon a like stipulation of the county; or the improvement may be made by joint contract. When municipal streets or alleys are widened or improved by the county, in the manner herein provided, and special benefits result therefrom to abutting property, the municipality shall collect such benefits in the manner now provided by law, and shall apply the amount thereof to its share, if any, of the cost of such improvement.
53 P.S. § 1835