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Lighting Master Plan and Street Lighting Conversion

The City of Cambridge initiated a planning study to improve the design and maintenance of its public lighting system. The effort was prompted by the purchase of approximately 5,000 street lights from the local utility company that had been operating them. Primary objectives of the study were to review current public lighting and establish design guidelines for new construction, review and recommend the content of the lighting inventory, and research and recommend emerging light sources and fixtures for evaluation in use.

 

To produce this master plan, WSP USA worked with a lighting committee of city staff from several departments including the Electrical Department, Historical Commission, Department of Public Works, and Community Development Department.

Following the initial study WSP provided preliminary testing and analysis of conversion of the city’s street lighting system to light emitting diode (LED) technology. We continued as sub-consultant for the final design of the conversion. A key feature of the new system will be adaptive controls to vary the light level locally based on expected traffic and pedestrian volumes. Additional pilot installations and tests allowed evaluation of system performance compared to the existing high pressure sodium (HPS) system and to current roadway lighting standards. Testing comprised taking readings on the roadway and in pedestrian areas, including vertical illuminance at face level, and evaluating light trespass impacts.
Public response to the initial installations was solicited by the City and has been positive, including response to the use of adaptive controls to dim the lighting system to half output when pedestrian volumes are expected to be low. The new system is expected to reduce power consumption to less than half of the present consumption of the HPS luminaires by controlling the light distribution, using criteria from current standards, and implementing adaptive controls. The new system is expected to have fewer maintenance requirements because of the light source’s longer life.