Code of Federal Regulations Title 23. Highways § 23.750.108 General provisions

(a) No sign may be permitted which attempts or appears to attempt to direct the movement of traffic or which interferes with, imitates or resembles any official traffic sign, signal or device.

(b) No sign may be permitted which prevents the driver of a vehicle from having a clear and unobstructed view of official signs and approaching or merging traffic.

(c) No sign may be permitted which contains, includes, or is illuminated by any flashing, intermittent or moving light or lights.

(d) No lighting may be permitted to be used in any way in connection with any sign unless it is so effectively shielded as to prevent beams or rays of light from being directed at any portion of the main-traveled way of the Interstate System, or is of such low intensity or brilliance as not to cause glare or to impair the vision of the driver of any motor vehicle, or to otherwise interfere with any driver's operation of a motor vehicle.

(e) No sign may be permitted which moves or has any animated or moving parts.

(f) No sign may be permitted to be erected or maintained upon trees or painted or drawn upon rocks or other natural features.

(g) No sign may be permitted to exceed 20 feet in length, width or height, or 150 square feet in area, including border and trim but excluding supports, except Class 2 signs not more than 50 feet from, and advertising activities being conducted upon, the real property where the sign is located.