The state highways and transportation commission is hereby authorized to make minor relocations in any state highway or any part thereof when in its opinion such minor relocations are necessary in the interest of safety to the traveling public or in the interest of economy and directness of route; provided, that no such minor relocations shall deviate from any designated point named in any law which may now or hereafter be in force; provided, however, the terms, powers and authority granted in this section shall apply only when the conditions exist as enumerated in sections 227.270, 227.280 and 231.100.