The board of commissioners may widen, repave or otherwise improve said municipal streets whenever the same is necessary to accomplish any of the purposes of sections 2920 and 2921 of this act. Whenever such improvement is made to a municipal street, the county may pay the total cost of such improvement, or the cost may be divided between or among the municipality or municipalities and the county. The contract for any such improvement may be taken by the county upon the stipulation by any municipality to pay its proportionate share of the cost, if any, upon the completion of the work, or it may be taken by any municipality upon a like stipulation of the county, or the improvement may be made by joint contract.
16 P.S. § 5922