Iowa Code Title VIII. Transportation [Chs. 306-330B] § 321.317. Signals by hand and arm or signal device

1. The signals required under the provisions of this chapter may be given either by means of the hand and arm as provided in section 321.318, or by a mechanical or electrical directional signal device or light conforming to the provisions of this chapter.

2. Directional signal devices shall be designed with a white, yellow or amber lamp or lamps to be displayed on the front of vehicles and with a lamp or lamps of red, yellow or amber to be displayed on the rear of vehicles. Such devices shall be capable of clearly indicating any intention to turn either to the right or to the left and shall be visible and understandable during both daylight and darkness from a distance of at least one hundred feet from the front and rear of a vehicle equipped therewith.

3. It is unlawful for any person to sell or offer for sale or operate on the highways of the state any vehicle subject to registration under the provisions of this chapter which has never been registered in this or any other state prior to January 1, 1954, unless the vehicle is equipped with a directional signal device of a type in compliance with the provisions of subsection 2. Motorcycles, motorized bicycles, and semitrailers and trailers less than forty inches in width are exempt from the provisions of this section.

4. When a vehicle is equipped with a directional signal device, such device shall at all times be maintained in good working condition. No directional signal device shall project a glaring or dazzling light. All directional signal devices shall be self-illuminated when in use while other lamps on the vehicle are lighted.

5. Whenever any vehicle or combination of vehicles is disabled or for other reason may present a vehicular traffic hazard requiring unusual care in approaching, overtaking or passing, the operator then may display on the vehicle or combination of vehicles four directional signals of a type complying with the provisions of this section relating to directional signal devices in simultaneous operation.