The assent of the legislature is hereby given to the provisions and requirements of the act of congress known as the federal-aid road act, approved July 11, 1916, entitled “An act to provide that the United States shall aid the states in the construction of rural post roads, and for other purposes.” The legislature likewise assents to all subsequent federal-aid acts, federal highway acts, federal-aid highway acts and the federal aid highway act of 1956 and all acts amendatory thereof or supplemental thereto.