In counties of the third, fourth, fifth, sixth, seventh and eighth class, in which a stream over which it may be necessary to build a bridge crosses a public road, and the building of the bridge requires the construction of an embankment or causeway leading to either end of such bridge, the erection of which embankment or causeway requires more expense than it is reasonable that one or more adjoining townships should bear, the bridge may, in the discretion of the county commissioners, be entered on record as a county improvement and constructed as county bridges are constructed.
Pennsylvania Legal Code