Gareth investigates the current state of play regarding lumen maintenance testing of outdoor lighting. This paper presents an analysis of the current street lighting test methods and discusses some possible alternatives to the current procedures. Talk by Dr Gareth John, Photometric and Optical Testing Services

1. Lumen Maintenance Testing of Outdoor
Lighting Installations
Dr Gareth John, Technical Director, Photometric
& Optical Testing
ILP Lighting Summit, 24th of September 2015

2. Maintenance Factor
• Need for maintenance-
• The luminance/illuminance initially provided by a lighting installation will
decrease gradually throughout the life of the installation.
• “Ratio of the average luminance/illuminance on the working plane after a certain
period of use of a lighting installation to the average luminance/illuminance
obtained under the same conditions for the installation considered conventionally
as new.” CIE Technical Report 154, “Maintenance of Outdoor Lighting Systems.
• Degradation is down to a combination of lamp depreciation, lamp failure and
accumulated dirt.

3. Maintenance Factor
MF = LLMF x LSF x LMF (x SMF)*
where LLMF = the lamp lumen maintenance factor;
LSF = the lamp survival factor;
LMF = the luminaire maintenance factor;
and where appropriate (e.g. pedestrian subways):
SMF = the surface maintenance factor.

4. Lamp Lumen Maintenance Factor

5. Lamp Survival Factor

6. Luminaire Maintenance Factors

7. Maintenance Factor and LEDs

8. Measurement of Maintenance Factor

9. TR28- Measurement of Road Lighting
Performance on site
• Based upon BS EN
13201-4, “Road
Lighting, Methods of
Measuring Lighting
Performance
• A practical guide to
onsite measurements
with calibrated
photometers

10. TR28- Measurement of Road Lighting
Performance on site
• A random sample of sites are checked, ideally once a month
• Multipoint measurement across a grid on the roadway
• Checked against software simulation

11. TR28- Measurement of Road Lighting
Performance on site
• Measurement conditions (from
13201-4:)
• The luminaire output should be
stable
• The effect of climate upon
measurement results must be
considered
• [Extraneous light and sources of
obstruction (parked cars, trees)
must be eliminated as far as
possible.

12. TR28- Measurement of Road Lighting
Performance on site (Obstructions)

13. TR28- Measurement of Road Lighting
Performance on site (Photometer)

14. TR28- Measurement of Road Lighting
Performance on site (Uncertainties)
• Ambient temperature- 25°C or 15°C?
• Moonlight- up to 0.3 lux
• Cloud cover
• Extraneous Light
• Luminous Intensity Distribution and angular errors
• Photometer- TR28 states ~6% at best

15. TR28- Luminous Intensity Distribution

16. TR28- Measurement of Road Lighting
Performance on site (Uncertainties)
• What can be controlled or eliminated?
• Variation in lamp type
• Variation in supply voltage
• Variation in lamp mounting and tilt
• Accuracy of light meters
• What can’t be accurately controlled:
• Access to area
• Climate conditions
• Obstructions
• Extraneous light
• Reflections from roadway

17. CSS Street Lighting Project 2007: Review of
Maintenance Factors
• Published in 2008
• Collaboration between the County Surveyors’
Society and the lighting industry
• Carried out in order to assess if maintenance
factors were accurate

18. CSS Street Lighting Project 2007: Review of
Maintenance Factors
• Sites selected at random
with at least two
luminaires from each site
• Testing for total lumen
output, carried out in a
photometric laboratory
• Luminaires tested for
light output before and
after cleaning

19. Laboratory Testing of Luminaire Maintenance
• Uncertainties:
• Environmental conditions- temperature can be controlled to within ±0.5°C and
wind speed to within ±0.2 m/s
• Moonlight- not applicable
• Cloud cover- not applicable
• Extraneous Light- not applicable
• Luminous Intensity Distribution and angular errors- not applicable because the
light distribution is integrated
• Use of spectroradiometer means light measurement errors are >2%
• Input voltage can be controlled to an accuracy of ±0.1 V

20. Laboratory Testing of Luminaire Maintenance
• Benefits-
• Elimination of unknown factors
• Repeatable
• Much lower level of uncertainty

21. Any Questions?
01242 701300