(a) The erection or maintenance of the following signs may be permitted within protected areas, outside informational sites:

(1) Class 3 signs which are visible only to Interstate highway traffic not served by an informational site within 12 air miles of the advertised activity;

(2) Class 4 signs which are more than 12 miles from the nearest panel within an informational site serving Interstate highway traffic to which such signs are visible.

(3) Signs that qualify both as Class 3 and 4 signs may be permitted in accordance with either paragraph (a)(1) or (2) of this section.

(b) The erection or maintenance of signs permitted under paragraph (a) of this section may not be permitted in any manner inconsistent with the following:

(1) In protected areas in advance of an intersection of the main-traveled way of an Interstate highway and an exit roadway, such signs visible to Interstate highway traffic approaching such intersection may not be permitted to exceed the following number:

The specified distances shall be measured to the nearest point of the intersection of the traveled way of the exit roadway and the main-traveled way of the Interstate highway.

(2) Subject to the other provisions of this paragraph, not more than two such signs may be permitted within any mile distance measured from any point, and no such signs may be permitted to be less than 1,000 feet apart.

(3) Such signs may not be permitted in protected areas adjacent to any Interstate highway right-of-way upon any part of the width of which is constructed an entrance or exit roadway.

(4) Such signs visible to Interstate highway traffic which is approaching or has passed an entrance roadway may not be permitted in protected areas for 1,000 feet beyond the furthest point of the intersection between the traveled way of such entrance roadway and the main-traveled way of the Interstate highway.

(5) No such signs may be permitted in scenic areas.

(6) Not more than one such sign advertising activities being conducted as a single enterprise or giving information about a single place may be permitted to be erected or maintained in such manner as to be visible to traffic moving in any one direction on any one Interstate highway.

(c) No Class 3 or 4 signs other than those permitted by this section may be permitted to be erected or maintained within protected areas, outside informational sites.