Morrisville UDO - June 2017 version

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Article 5: Development Standards
Section 5.15. Exterior Lighting
5.15.3. Parking and Outdoor Lighting Light Levels
Morrisville, NC June 23, 2017
Unified Development Ordinance Page 5-141
C. Measurement of Light Levels
Light levels are specified, calculated, and measured in maintained foot-candles (i.e., include a
maintenance factor for dirt build-up and lamp lumen depreciation) unless specified otherwise.
Measurements of light levels shall be taken with a light meter that has been calibrated within two years.
They shall be taken at finished grade (ground level), with the light-registering portion of the light meter
held parallel to the ground and pointing up. The meter shall have cosine and color correction and an
accuracy tolerance of no greater than plus or minus five percent.
5.15.3. Parking and Outdoor Lighting Light Levels
A. Light Levels and Uniformity Ratios for High Pressure Sodium (HPS) and Metal Halide (MH)
Lighting
Exterior light levels for high pressure sodium (HPS) and metal halide (MH) lighting shall comply with
standards in Table
for the type of lighting.
Table
Type of Lighting
Light Level (foot-candles) [1][2] Average Light Level to
Minimum Light Level
Uniformity Ratio Maximum Average Minimum
Anchor Tenant in a Major or
Neighborhood Shopping Center
n/a 4.0 0.2 4:1
Loading Dock n/a 3.0 0.2 4:1
Nonresidential Parking Lot n/a 3.0 0.2 4:1
Vehicle Sales 20.0 n/a 0.2 5:1
Vehicular Canopy 20.0 n/a 0.2 4:1
Notes: n/a = not applicable
[1] Maximum and average light levels shall be a horizontal measurement at grade or ground level of light level points
on a ten-foot by ten-foot point-by-point layout grid in the overall lighted area. They shall be a not-to-exceed value
measured or calculated using only the area of the site intended to receive illumination.
[2] Measurements and calculations for a new system (after 100 hours of burn-in) shall be multiplied by a maintenance
factor of not greater than 0.72 foot-candles for high pressure sodium lighting and 0.64 for metal halide lighting to
determine compliance with the standards in this table. For example, if a maximum point measurement of 23 foot-candles
was taken on a vehicle sales lot for a new metal halide lighting system, then 23 x 0.64 = 14.72 foot-candles.
B. Light Levels and Uniformity Ratios for Light Emitting Diode (LED) Lighting
Exterior light levels for Lighting Emitting Diode (LED) lighting shall comply with standards in Table
for the type of
lighting.