After any such contract has been entered into, the county commissioners, in conjunction with the municipality, shall have prepared plans and specifications of the entire work and shall advertise for bids and award the contract to the lowest responsible bidder. Such contract shall provide that the county shall pay its certain part of such bridge or viaduct directly to the contractor. The contractor shall have a right of action against the county for the part of the contract which the county agrees to pay.
16 P.S. § 5855