At the conclusion of such hearing the secretary of transportation shall consider the evidence taken at such hearing and shall make specific findings in the case of each proposal or counterproposal and shall adopt a plan with such modifications, if any, he deems proper and necessary. The secretary may order the adoption of any proposal or counterproposal in its entirety or in part, or may modify or reject any such proposal or counterproposal. The secretary's findings or order shall be in writing and copies thereof shall be served by United States mail upon all persons having entered a written appearance at such hearing and upon the county commissioners of the county affected and/or the mayor of the city or town affected. The secretary shall also cause a resume of such plan to be published once each week for two weeks in one or more newspapers of general circulation within such county, city or town beginning not less than ten days after the mailing of such findings and order. Such determination by the secretary shall become final within thirty days after such mailing unless a review is taken as by statute provided. In case of an appeal by any party the order shall be final as to all parties not appealing.