Signs within six hundred and sixty feet of the nearest edge of the right-of-way which are visible from the main traveled way of the primary system within commercial and industrial areas and whose size, lighting, and spacing are consistent with the customary use of property for the effective display of outdoor advertising as set forth in this section may be erected and maintained: PROVIDED, That this section shall not serve to restrict type 3 signs located along any portion of the primary system within an incorporated city or town or within any commercial or industrial area.

(1) General: Signs shall not be erected or maintained which (a) imitate or resemble any official traffic sign, signal, or device; (b) are erected or maintained upon trees or painted or drawn upon rocks or other natural features and which are structurally unsafe or in disrepair; or (c) have any visible moving parts.

(2) Size of signs:

(a) The maximum area for any one sign shall be six hundred seventy-two square feet with a maximum height of twenty-five feet and maximum length of fifty feet inclusive of any border and trim but excluding the base or apron, supports and other structural members: PROVIDED, That cut-outs and extensions may add up to twenty percent of additional sign area.

(b) For the purposes of this subsection, double-faced, back-to-back, or V-type signs shall be considered as two signs.

(c) Signs which exceed three hundred twenty-five square feet in area may not be double-faced (abutting and facing the same direction).

(3) Spacing of signs:

(a) Signs may not be located in such a manner as to obscure, or otherwise physically interfere with the effectiveness of an official traffic sign, signal, or device, obstruct or physically interfere with the driver's view of approaching, merging, or intersecting traffic.

(b) On limited access highways established pursuant to chapter 47.52 RCW no two signs shall be spaced less than one thousand feet apart, and no sign may be located within three thousand feet of the center of an interchange, a safety rest area, or information center, or within one thousand feet of an intersection at grade. Double-faced signs shall be prohibited. Not more than a total of five sign structures shall be permitted on both sides of the highway per mile.

(c) On noncontrolled access highways inside the boundaries of incorporated cities and towns not more than a total of four sign structures on both sides of the highway within a space of six hundred sixty feet shall be permitted with a minimum of one hundred feet between sign structures. In no event, however, shall more than four sign structures be permitted between platted intersecting streets or highways. On noncontrolled access highways outside the boundaries of incorporated cities and towns minimum spacing between sign structures on each side of the highway shall be five hundred feet.

(d) For the purposes of this subsection, a back-to-back sign and a V-type sign shall be considered one sign structure.

(e) Official signs, and signs advertising activities conducted on the property on which they are located shall not be considered in determining compliance with the above spacing requirements. The minimum space between structures shall be measured along the nearest edge of the pavement between points directly opposite the signs along each side of the highway and shall apply to signs located on the same side of the highway.

(4) Lighting: Signs may be illuminated, subject to the following restrictions:

(a) Signs which contain, include, or are illuminated by any flashing, intermittent, or moving light or lights are prohibited, except those giving public service information such as time, date, temperature, weather, or similar information.

(b) Signs which are not effectively shielded as to prevent beams or rays of light from being directed at any portion of the traveled ways of the highway and which are of such intensity or brilliance as to cause glare or to impair the vision of the driver of any motor vehicle, or which otherwise interfere with any driver's operation of a motor vehicle are prohibited.

(c) No sign shall be so illuminated that it interferes with the effectiveness of, or obscures an official traffic sign, device, or signal.

(d) All such lighting shall be subject to any other provisions relating to lighting of signs presently applicable to all highways under the jurisdiction of the state.