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Streetlight Selection Design Considerations

Street light extending over street

The streetlight catalogue is a design palette for project designers who can choose from the fixture options presented based on neighborhood aesthetics, design continuity between neighborhoods, street type and photometric requirements. The fixture options in the catalogue were selected because of their energy efficient and long life light sources, good spectral distribution, limited glare or light trespass, design aesthetics, and ability to reduce maintenance costs.

Efficient Technology
For both energy efficiency and reduced maintenance costs, the most promising technological advancements at this time can be found in LED and metal halide light sources. Besides several existing HPS fixtures, the City has limited fixture selection to those using LED and metal halide light sources.

Luminous Efficacy (Lumens/Watt)
It is our goal to use the most energy efficient light sources possible on San Francisco streets. A measure of light source efficiency is lamp efficacy, which is measured in lumens (light output) per watt. The lumens/watt calculation indicates how well a source produces visible light. The overall light output that exits the fixture is reduced by internal reflectors and other surfaces inside the fixture that absorb the light. Since light fixtures with traditional light sources require internal reflectors to direct the light outwards, but LED fixtures do not, the efficacy of LED fixtures is not a comparable measure of how well a fixture illuminates the street. The specific luminous efficacy of the sources used in the catalogue is not listed because most of the new fixtures use LED light sources which deliver illumination to the street surface differently from traditional sources.

Maintainability and Durability
All fixtures selected for the catalogue have been reviewed for ease of maintenance and durability. When available from the manufacturer, tool-less accessibility has been provided or side access doors to ballast compartments are included. Fixture design aspects such as the presence of wire quick disconnects, lens material, fixture weight and ease of handling, were considered.

Long life light sources have reduced maintenance requirements due to less frequent outages. New fixtures selected for the catalogue include long life 50,000-hour LED to 100,000-hour LED.

The light fixture poles must be durable. Poles for the fixtures in the catalogue are made of steel, the only exceptions being unique pedestrian scale fixtures where heavy gauge aluminum is provided. The pole bases accommodate bolt circles between 10” and 11.5” which match the bolt circle sizes of SFPUC temporary light poles that are used when a light fixture pole is removed for servicing. In addition, clamshell base cover designs and mechanical attachment decorative pole features were favored.

All catalogue light fixtures are listed by either Underwriters Laboratories (UL) or another testing laboratory recognized by the U.S. Department of Labor Occupational Safety & Health Administration (OSHA) Nationally Recognized Testing Laboratories (NRTL) Program. The fixtures have minimum Ingress Protection Ratings of IP65 or equivalent wet location ratings by a recognized testing laboratory.

The fixture manufacturer listed for each fixture in the catalogue sets the minimum acceptable quality standards. Only fixtures provided by well-established manufacturers – 15 years minimum operation – are included. The fixtures are expected to last 35 years before needing replacement due to natural wear and tear.

Fixture Styles
Part of San Francisco’s charm is the prevalence of Victorian and Edwardian architecture juxtaposed amongst styles of later time periods. The historic-style light fixtures chosen for the catalogue complement the Victorian and Edwardian periods yet are timeless enough to blend harmoniously with other architectural styles. Contemporary fixture styles are also included in the catalogue for those projects that call for a more distinctly modern look. The contemporary fixtures were chosen for their simple timeless designs and cutting edge technology.

 

Last updated: 6/1/2017 9:48:53 AM