1. (1) Agreements between the Tennessee Department of Transportation and the United States Department of Transportation, Federal Highway Administration. (This space intentionally left blank.)

   1. (a) Original Agreement (November 11, 1971)
   2. (b) Supplemental Agreement (October 16, 1984)

2. (2) Brightness Standards for Changeable Message Signs with a Digital Display T.C.A. § 54-21-119(h) establishes the brightness standards for changeable message signs with a digital display, as follows:

   1. (a) All changeable message signs installed on or after July 1, 2014, must come equipped with a light-sensing device that automatically adjusts the brightness in direct correlation with ambient light conditions.
   2. (b) The brightness of light emitted from a changeable message sign must not exceed 0.3 foot candles over ambient light levels measured at a distance of one hundred fifty feet (150’) for those sign faces less than or equal to three hundred square feet (300 sq. ft.), measured at a distance of two hundred feet (200’) for those sign faces greater than three hundred square feet (300 sq. ft.) but less than or equal to three hundred eighty-five square feet (385 sq. ft.), measured at a distance of two hundred fifty feet (250’) for those sign faces greater than three hundred eighty-five square feet (385 sq. ft.) and less than or equal to six hundred eighty square feet (680 sq. ft.), measured at a distance of three hundred fifty feet (350’) for those sign faces greater than six hundred eighty square feet (680 sq. ft.), or subject to the measuring criteria in the applicable table set forth in subdivision (h)(4).
   3. (c) Any measurements required pursuant to this subsection (h) must be taken from a point within the highway right-of-way at a safe distance from the edge of the traveled way, at a height above the roadway that approximates a motorist’s line of sight, and as close to perpendicular to the face of the changeable message sign as practical. If perpendicular measurement is not practical, valid measurements may be taken at an angle up to forty- five (45) degrees from the center point of the sign face. If measurement shows a level above that prescribed in subdivision (h)(4), the exact calculations must be provided to the sign permit holder.

   4. (d) In the event it is found not to be practical to measure a changeable message sign at the distances prescribed in subdivision (h)(2), a measurer may opt to measure the sign at any of the alternative measuring distances described in the applicable table set forth in this subdivision (h)(4). In the event the sign measurer chooses to measure the sign using an alternative measuring distance, the prescribed foot candle level above ambient light must not exceed the prescribed level, to be determined based on the alternative measuring distances set forth in the tables in subdivisions (h)(4)(A), (B), (C), and (D), as applicable. For any measuring distance between the alternative measuring distances set forth in the following tables, the prescribed foot candle level above ambient light must not exceed the interpolated level derived from the following formula: [12 = (D2<2>/01<2>) x 11] Where l1 = the prescribed foot candle level above ambient light for the measuring distance listed in the tables, l2 = the derived foot candle level above ambient light for the desired measuring distance, D1 = the desired measuring distance in feet, and D2 = the alternative measuring distance in feet listed in the tables, as follows:

      1. 1. For changeable message signs less than or equal to three hundred square feet (300 sq. ft.): Alternative Measuring Distance: Prescribed Foot Candle Level: 100 0.68 125 0.43 150 0.3 200 0.17 250 0.11 275 0.09 300 0.08 325 0.06 350 0.06 400 0.04
      2. 2. For changeable message signs greater than three hundred square feet (300 sq. ft.) but less than or equal to three hundred eighty-five square feet (385 sq. ft.): Alternative Measuring Distance: Prescribed Foot Candle Level: 100 1.2 125 0.77 150 0.53 200 0.3 250 0.19 275 0.16 300 0.13 325 0.11 350 0.1 400 0.08
      3. 3. For changeable message signs greater than three hundred eighty-five square feet (385 sq. ft.) but less than or equal to six hundred eighty square feet (680 sq. ft.): Alternative Measuring Distance: Prescribed Foot Candle Level: 100 1.88 125 1.2 150 0.83 200 0.47 250 0.3 275 0.25 300 0.21 325 0.18 350 0.15 400 0.12
      4. 4. For changeable message signs greater than six hundred eighty square feet (680 sq. ft.): Alternative Measuring Distance: Prescribed Foot Candle Level: 100 3.675 125 2.35 150 1.63 200 0.92 250 0.59 275 0.49 300 0.41 325 0.35 350 0.3 400 0.23 425 0.2 450 0.18 500 0.15
   5. (e) The brightness standards established in T.C.A. § 54-21-119(h) apply to all changeable message signs located in this state operated pursuant to a permit issued by the Commissioner. (This space intentionally left blank.)

3. (3) Illustrations

   1. (a) Abandoned Devices
   2. (b) Measurement of Adjacent Area at Interchanges
   3. (c) Destroyed Non-Conforming Outdoor Advertising Device
   4. (d) Device Types: Double-Faced
   5. (e) Device Types: Back-To-Back
   6. (f) Device Types: V-Type
   7. (g) Device Types: Stacked Display
   8. (h) Unzoned Commercial or Industrial
   9. (i) Sign Face Size & Parts
   10. (j) Sign Face Size
   11. (k) Incorrect Sign Face Size
   12. (l) Sign Spacing: Measurement Methods
   13. (m) Sign Spacing: Measurement Methods
   14. (n) Sign Spacing: Measurement Methods
   15. (o) Sign Spacing: Measurement Along A Curve
   16. (p) Spacing Exception
   17. (q) Ramp Control: Outside the City Limits
   18. (r) Sign Spacing: Not Fully Controlled Access Control
   19. (s) On-Premises Device
   20. (t) Vegetation Control: Example Only
   21. (u) Vegetation Control Removal Guide

Authority: T.C.A. § 54-21-111. Administrative History: Transfer from chapter 1680-02-03 and amendments filed February 14, 2024; effective May 14, 2024.