Chapter 14 - Lighting

14.5. Design Considerations

14.5.5. Interchange Lighting

High mast lighting shall be used for interchange lighting unless the location has constraints on the pole height such as near airport boundaries.  Conventional lighting may be used in the areas determined to have height constraints.

At interchanges, the high mast poles shall have 100-ft. nominal mounting height.  The high mast luminaries should be 1,000 Watt. Lower wattage luminaires may be utilized if satisfactory justification is first provided to GDOT. The lighting designer shall provide an optimum and cost effective lighting design for GDOT ’s approval.

High mast lighting shall be provided to cover a minimum of 1,000-ft. from the farthest gore point on exit/entrance ramp.  High mast lighting shall be provided to cover the distance to the point where the travel lane and taper is 12-ft. but shall not be less than 1,000-ft. from the gore point. (see Figure 14.1. Example of a Lighting Gore Detail). High mast luminaries with type V symmetrical distribution are preferred.  Other types of light distributions may be used to accomplish proper roadway illumination or to avoid spillage on adjacent properties.  up to and including the use of offset luminaires.  

Figure 14.1. Example of a Lighting Gore Detail

Shields shall be used to control light spillage on residences or other areas where the spilled light may be considered objectionable.  The lighting designer needs to consider this type of impact to surrounding areas and land uses when developing the proper lighting system.

For high mast pole foundations, design analysis shall be performed.  Soil borings shall be done at each proposed location of the high mast pole and the results used in the foundation design.  The high mast pole foundation design shall be approved by the GDOT Office of Bridge Design prior to installation.  High mast light poles located on a 2:1 or greater slope shall be provided with maintenance platforms.

All underpasses within the illuminated limits of the interchange shall maintain the same illuminance levels as the adjacent roadway.  This may require the installation of underpass luminaires.