The Chief of Police may cause markers, buttons, or signs to be placed within or adjacent to intersections, and thereby require and direct, as traffic conditions require, that a different course from that specified by the State law be traveled by vehicles turning at intersections, and when markers, buttons, or signs are so placed no driver of a vehicle shall turn a vehicle at an intersection other than as directed and required by the markers, buttons, or signs, including right-hand turns at intersections with automatic traffic signals.
(Code of Iowa, Sec. 321.311)