Take the Streetlight Survey

PAR members may want to take this survey on proposed SF streetlights:  

http://www.surveymonkey.com/SFStreetlights


Hi everyone,

Last week, one of the folks on the SF Smart Lighting mailing list brought this survey on decorative street lights to my attention: 
http://www.surveymonkey.com/SFStreetlights 

By way of helping to provide information regarding the comparative light pollution aspects of the fixtures being considered, I decided to write up some commentary that may be useful for you in taking the survey.

- Fixture Alternate A
- Lamp Type: High-pressure sodium
This is a typical 'acorn' type fixture.  Although the lamp is likely recessed into the opaque cap, the prismatic bowl does allow some uplight.  With low mounting heights and/or high luminance lamps, these can be quite glary.  The use of HPS, at 2100K CCT, helps decrease the perception of glare however, compared to other lamp types.  Here in S.F. these types of fixtures are usually installed 'bare' without a shade or 'hat' to limit glare and uplight.  By contrast, Honolulu uses the 'hatted' version of this design to reduce glare and stray uplight.  Take a look at the street view on Google maps of Kalakaua Ave. and Kuhio Ave. in Waikiki to see examples.

- Fixture Alternate B
- Lamp Type: High-pressure sodium
Very poor, light polluting design.  It permits significant amounts of uplight and glare for no reason.

- Fixture Alternate C
- Lamp Type: High-pressure sodium
I call this fixture 'the glass salad bowl'.  Similarly to alternative A, this fixture is not fully shielded and thus does produce uplight, and does present glare.  Not my favorite.

- Fixture Alternate D 
- Lamp Type: High-pressure sodium
Similar concerns to alternate B, this light produces significant uplight through its prismatic reflector and apparently translucent top.  And of course is very glary.  Very poor design.

- Fixture Alternate E
- Lamp Type: High-pressure sodium
Similar factors apply as with alternate A, above.

- Fixture Alternate F
- Lamp Type: LED
This is a modern fully-shielded fixture.  Reasonably good glare control, and when installed correctly with the LED array horizontal, virtually no uplight.  As noted before, it is most preferable to use LED's with minimal blue output.  Color temperatures in the 2700K - 3500K range minimize blue light output while still producing a natural looking white light.  Alas, I don't think this fixture is available yet with such warm-white color LED's.

- Fixture Alternate 1
- Lamp Type: LED
The sketch doesn't clearly indicate the optics involved.  Such a design in which the glass lens is simply a clear bowl (not prismatic or textured, and preferably with antireflective coatings) do well in terms of minimizing uplight -- assuming, that is, that the LED array is recessed in an opaque top.  I believe several manufacturers are also offering a similar design, but with a flat lens rather than a clear bowl.  A flat lens is even better from the point of view of uplight control.

- Fixture Alternate 2
- Lamp Type: Ceramic metal halide
This is an excellent fixture from the point of view of uplight.  It is fully shielded with a flat lens and with the recessed lamp probably also controls glare pretty well.  Metal halide is not my favorite source, as it tends to be rather high CCT.  Similar fixtures are available with LED's.

- Fixture Alternate 3
- Lamp Type: LED
Also an excellent fixture from the point of view of uplight.  It is fully shielded and appears that it would provide quite good glare control.  Same issues regarding minimizing blue light emissions from LED's as fixture F, above.

- Fixture Alternate 4
- Lamp Type: LED
       --and--
- Fixture Alternate 5
- Lamp Type: LED
Also excellent fixtures from the point of view of uplight.  They are fully shielded and probably have good glare control.  Same issues regarding minimizing blue light emissions from LED's as fixture F, above.

- Fixture Alternate 6
- Lamp Type: LED
I haven't seen a design like this before, so it's hard to guess how well it does in terns of uplight and glare.  I'd really want to know the BUG score numbers on this one before giving it an endorsement.

- Fixture Alternate 7
- Lamp Type: LED
Looks pretty good as far as uplight.  Fully shielded and probably has good glare control.  Same issues regarding minimizing blue light emissions from LED's as all LED fixtures in survey.  The one thing that concerns me here is that it looks like a lot of the light is hitting the support arms, which is not only wasted light but also is then be scattered upward.  Granted it's a minor point but something to note.


Thanks,
-DG



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