This report describes a review of luminaire maintenance factors, which together with lamp luminous flux maintenance factors produce the maintenance factor to be used with a particular lamp and luminaire combination in the design of street lighting. Current methods were found to be based on research carried out in the 1970s, since when pollution levels and equipment designs have changed. Most documents refer to the current British Standard, BS 5489:2003.
The review comprised desktop research of relevant publications and standards, questionnaires to local authorities on their current practice, and the testing of luminaires removed from site to measure the actual light reduction over a period in service. The questionnaire results revealed a generally unscientific approach to setting pollution categories, often resulting in excessive conservatism. For the experimental work, luminaires with different bowl types and mounting heights were taken from locations in different environmental zones with varying pollution and traffic levels. All of the luminaire measurements revealed that loss of light output was less severe than predicted by the current standard.
Based on these findings, it is proposed that higher factors should be adopted. A revised table of “worst-case” maintenance factors for the different environmental zones, and four cleaning intervals is given. However it is considered that, in order to give greater confidence in the proposed factors, further work is required to create a wider range of results. The adoption of the proposed higher maintenance factors will result in designs requiring lower initial luminous flux, thus saving energy and cost and reducing typical CO2 emissions.
Other titles in this series:
SL1 ‘Review of the class and quality of street lighting’. G I Crabb, R Beaumont and D Webster. TRL Published Report PPR380. 2008
SL2 ‘Invest to save – sustainable street lighting’. P Fox. Mouchell. 2008
SL4 ‘The use of passively safe signposts and lighting columns’. GL Williams, J V Kennedy, J A Carroll and R Beesley. TRL Published Project Report PPR342. 2008
SL5 ‘Review of the lighting requirements for traffic signs and bollards’. J Cooper, K Stafford, P Owlett and J Mitchell. TRL Published Project Report PPR382. 2008
SL6 Guidance on the lighting requirements for traffic signs and bollard. J Cooper and J Mitchell. TRL Published Project Report PPR383. 2008

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