University District Lighting Project and Energy Conservation


Executive Summary

The University District joint lighting project by the University of Illinois and Cities of Urbana and Champaign is an opportunity to have a big impact both environmentally and fiscally. As the University of Illinois examines ways to save energy costs per recent statements from President White and Chancellor Herman, this discussion is timely. Professor Gary Cziko’s recent presentation on lighting in Campustown (http://www.uiuclights.notlong.com) to both CUUATS and the Urbana City Council has raised a number of interesting points and generated substantial discussion in the community. Additionally, Ameren IP, the local power supplier, has asked for a 46% rate increase to cities for street lighting. As a capital project, there are long term issues and implications about choices made for lighting and lighting design that need to be discussed in advance of the release of the Request for Proposals before we commit ourselves to something that will last many years and influence future designs. We have examples of communities that have taken steps in a variety of areas that have huge payoffs 10 and 20 years down the road.

This is an opportunity where all sides can be satisfied. Even though research indicates that greater amounts of light make people feel safer without actually reducing levels of street crime, it's probably not worth much time arguing about this because we know effective lighting is good for business, gets people out on the street, and makes pedestrians visible to vehicles at busy locations. At the same time, it isn’t necessary to turn night into day to create a safe environment. There are recommended design levels for lighting from the IESNA (Illuminating Engineering Society of North America) that match activity to environmental zone. Further, we don’t want to create a shouting effect where everyone thinks that we need to make things louder or brighter just to be heard or seen. Overly bright light creates a safety hazard as we need to remember that the human eye responds quickly to bright but is slow to adapt to dark. This puts people at risk when moving or driving from an overly bright area to normal evening lighting.

There's clearly money to be saved on energy costs by using properly designed lighting and even more money if used together with energy saving bulbs. About 40% of the City of Urbana’s energy costs are related to lighting and the University of Illinois is faced with laying off staff to pay for increased energy costs. The cities and the University should not go forward with any more lighting until they can use LED or equivalent energy saving type lighting in full cutoff fixtures. Properly designed, effective lighting doesn’t create harsh shadows or serious glare and at the same time, is not light polluting. By using full cutoff fixtures, which are now used in many locations (and even required by some building codes), the two forms of light pollution (light trespass and sky glow) are reduced while keeping the light below the horizontal plane. This in turn means that less energy is needed for the same amount of light on the streets and sidewalks since no energy is sent uselessly above the light fixture. Instead, by using reflectors, any energy above the horizontal plane is directed downward allowing for the same amount of light for about half the energy of a similar, non-cutoff fixture.

The possibility of balancing the combinations of lights used in LED's to enhance night vision is intriguing. From a safety point of view, this could be a major selling point. We might be able to have lighting that isn’t as bright (and hence saves energy) but is more effective for both pedestrians and drivers. We have examples of cities that are saving money and the industry is maturing quickly with LED’s appearing in many useful places. A variety of LED Street lights are beginning to show up on the market place with improvements appearing frequently. It may be that a short delay will bring substantial new technology into play that would allow us to use LED technology in our new designs. New designs should at least incorporate the possibility of LED retrofit and allow for switchover should LEDs become practical during the life of the project.

For environmental reasons, streetscape projects should use, at a minimum, LEED (Leadership in Energy and Environmental Design) for guidance. This green building rating tool developed by the US Green Building Council (USBGC) has a credit for both controlling light pollution and generating light efficiently.  Each credit has an "intent" (tells you what is important), "requirements" (how to calculate if you've earned the credit or not) and "technologies strategies" (how to earn the credit). There are many communities and companies and at least 9 federal agencies who have adopted LEED.  The University of Illinois uses LEED and its use is now mandated by the State of Illinois (http://www.cdb.state.il.us/green_initiatives.shtml). This implies that the University should be using LEED for its new streetscapes. Nearby, the City of Normal, Illinois has adopted LEED for its Uptown projects including its streetscape: http://www.normal.org/Uptown/LEED.asp. To design and install exterior lighting in Urbana that cannot meet the rather modest requirements of LEED would be glaringly inconsistent with Urbana's stated goals for sustainable development and inconsistent with the Mayor Laurel Prussing’s signing of the U.S. Conference of Mayors' Climate Protection Agreement.

This document includes a summary of research findings found by and ideas provided by those listed at the end. Below we briefly discuss (with relevant links) LED lighting, Light Pollution, LEED Certification, a list of Lighting and Safety Studies, some links to what other communities are doing, and a discussion of issues by two contributing members. A live version of this document, which we hope to keep updating, can be found at http://www.charliesmyth.org/docs/lighting.html.


LED Lighting

The DarkSky.org website rates and lists appropriate light fixtures that avoid light pollution.  The brightness of the light has to match the pole height to provide adequate lighting for the activity (usually measured in foot candles or lux).  There are a number of LED Streetlights available: http://www.darksky.org/lighting/ lists possibilities and Dark-sky friendly lighting products are linked to at the bottom of this web page: http://www.darksky.org/programs/fixture-seal-of-approval.php.

An LED fixture (manufactured by Beta, http://www.betaled.com/default.htm) is being demonstrated at the International Dark-Sky Association headquarters in Tucson. It has lenses for each separate LED that direct the light in a desired pattern. The demo model was designed to be mounted in a location where more light was wanted on one side than the other (e.g., street vs. sidewalk sides) and it does just that. It can be imagined that the same lens technology could be used to spread out more evenly the light in those locations where desired. Beta is also involved in lighting projects and test sites around the country (http://www.betaled.com/gallery.htm).

The Illuminating Engineering Society of North America is the body that provides “Recommended Practices”, that is, guides for design practice, not necessarily 'standards' for lighting for different activities (http://www.iesna.org). They have lists of LED light manufacturers as well. The only current manufacturer listed on the IESNA site for LED lights, on high poles can be found at http://www.lithonia.com/NightTimeFriendly/AreaLuminaires.asp.

A web search for LED street lights finds http://www.iqled.com which has a bulb listed as “Retrofit High Power LED Streetlight 28W 2,100 lm - 85-265VAC, 12/25VDC SP90, 28w, 2,100lm, High Power LED Streetlight Source” and an advertisement  in Architectural and Civil Engineering Products:”LED Streetlights meet IES street lighting standards. February 17, 2004 - Series M400 CobraHead-Styled LED Streetlights shine light at ground level, eliminating unwanted glare, light trespass, energy waste, and sky glow. Containing 400 Warm Incandescent-White LEDs, cluster lamps draw 19 W, emit 3,200 K, and offer over 100,000 hr of life. Type 1 lamps have to be hardwired into cobra head fixtures, while Type 2 lamps feature male 39 mm mogul bases that screw into socket of fixture. Standard voltage is 120 Vac.”

Deb Lovig, CREE ( Deb_Lovig@cree.com) wrote:

We make only the LED components (http://www.cree.com), not the full fixture. I am attaching a list of LED fixtures makers we can recommend. I don't know if they are IDA approved but they are very good fixtures. I hope this is helpful. www.ledcity.org/fixture-contacts.html.

Most of the LED fixtures makers offer poles of different lengths or an attachment option for an existing pole. It's best to contact several directly to get product specs and comparison information.

We simply attached LED fixtures to existing poles in our parking lot last month. However, the new pole designs are very nice and if you are buying poles anyway, I'd look into the options from the LED makers.

It should be noted that there are many manufacturers of specification grade LEDs. The "LEDCity" program is a marketing invention of one LED manufacturer.

 

A Canadian firm, Elumen, has an LED street light with more uniform light distribution: http://www.elumen.ca/led_streetlight_technology.html and boasts that it’s technology pays for itself in 2 to 5 years.

 

There is solar powered LED Pedestrian lighting from Osram:  http://www.osram.com/appscom/cgi-bin/press/archiv.pl?id=608

Light Pollution Issues

Local articles on light pollution with a nice introduction to the various aspects of good and bad lighting:
            http://environmentalalmanac.blogspot.com/2005/03/light-pollution.html and             http://www.astro.uiuc.edu/~uias/lightpollution/

These local photos make the point very well:
            http://www.astro.uiuc.edu/~uias/lightpollution/pics/panorama/

            http://bi-staff.beckman.uiuc.edu/~melockwo/lp/lp.html

New Yorker article on light pollution:            http://www.newyorker.com/reporting/2007/08/20/070820fa_fact_owen

Website on light pollution and measures to combat it from a California perspective:             http://www.skykeepers.org/
includes links to municipal codes in California, such as Oakland's requiring full cut-off luminaries and glare reduction.

Photos of dark-sky friendly lighting here:
            http://www.darksky.org/programs/awards-2005.php

LEED Explanation

There are several different LEED rating tools.  For the LEED-NC (New Construction) tool, the credit is Sustainable Sites Credit 8, Light Pollution Reduction. The LEED-NC rating tool can be found at: http://www.usgbc.org/DisplayPage.aspx?CMSPageID=220
(see page 23 of this file:  http://www.usgbc.org/ShowFile.aspx?DocumentID=1095).

The LEED criteria for exterior lighting light pollution represent a minimum level of control of light pollution and energy efficiency and much stricter criteria exist. First, the International Dark-Sky Association approves only those light fixtures that emit no light above 90 degrees whereas LEED permits 2%, 5% and 10% of light to be emitted above 90 degrees in low, moderate and high lighting zones, respectively. Second, LEED permits 80% of the allowable light power density specified by ASHRAE whereas some other criteria, such as those required by the U.S. Department of Energy to qualify for tax reductions for lighting projects, require as little as 50% of the allowable ASHRAE power consumption maximum.  LEED is the least stringent of approaches (and hence, least effective) for saving energy and minimizing light pollution.

The draft version of LEED-ND (Neighborhood Development) is probably more relevant: http://www.usgbc.org/DisplayPage.aspx?CMSPageID=148. For this rating tool, we care about "Green Construction and Technology credit 20 - Light Pollution Reduction".  See page 141 of:  http://www.usgbc.org/ShowFile.aspx?DocumentID=2845.

The part about using LEED that people don't understand well is that the design team PICKS which credits they want to earn to achieve a rating.  There are Certified, Silver, Gold and Platinum ratings available depending on how many credits the team earns.   Here's a chart made for the Army:  https://eko.usace.army.mil/fa/sdd/leed/?syspage=Documents&id=33814 .
They require project teams to earn silver, but the only credits that are required by federal or Army policy are dark blue. The green credits are considered relatively easy to earn, and the Light Pollution credit is one of them.

We recommend project teams use the charrette checklist found at https://eko.usace.army.mil/fa/sdd/leed/?syspage=Documents&id=33810 at the beginning of a project to identify which credits they want to earn to get the rating they need to get.  (It has Army guidance embedded in it.) 

The light pollution credit should be chosen because it really wouldn't cost any more, you just have to pick lights that comply with the rules instead of lights that pollute.  The easiest way to comply with the requirements is probably to pick an IDA approved light fixture, and then to design the light scheme so it complies with the LEED Light Pollution requirements.

US Green Building Council Documents on federal, state, and local governments including various schools can be found at:  http://www.usgbc.org/DisplayPage.aspx?CMSPageID=1780 and other useful documents at: https://www.usgbc.org/ShowFile.aspx?DocumentID=1741

New energy-efficient, environmentally-friendly guidelines for state construction projects have been adopted (http://www.cdb.state.il.us/green_initiatives.shtml) that will meet strict national “green” building standards, reduce the state’s energy usage, and make state buildings better for those who work in them and the area surrounding them. The Green Building Guidelines for State Construction, developed by the Illinois Green Building Advisory Committee, mandate that all new state-funded building construction and major renovations of existing state-owned facilities are required to meet current Leadership in Energy and Environmental Design (LEED) standards that are practical for that project. The Capital Development Board (CDB), which manages all state construction, repair and renovation projects, developed the new guidelines and will oversee their implementation. The guidelines may be accessed at www.cdb.state.il.us.


Lighting and Safety Studies

An interesting paragraph from http://www.darksky.org/resources/information-sheets/is027.html:

“It appears that at Wesleyan there is no statistically significant evidence that outdoor lighting forms any deterrent to crimes of sexual assault. This supports the similar findings at a national level by a number of studies; the best known of which is probably the National Evaluation Program, Phase 1 Report, funded by the Law Enforcement Assistance Administration, U.S. Department of Justice (see Information Sheet No. 63). The conclusion of that report is that "there is no statistically significant evidence that street lighting impacts the level of crime", although it is recognized that increased lighting of almost any kind, good or bad, reduces the fear of crime. It is in society's interest to realize that feeling safe and being safe are not always the same, and different solutions may be needed to satisfy each condition. I believe that society would choose to be safe rather than just feel safe.”

 

Some resources on crime and lighting:
http://www.darksky.org/news/newsletters/50-59/nl59.html
US Department of Justice Study:  http://www.darksky.org/resources/information-sheets/is063.html
http://www.darksky.org/resources/information-sheets/is051.html
 http://crimeprevention.rutgers.edu/brochures/lighting2/lighting.htm
More British and American studies:

 http://www.homeoffice.gov.uk/rds/prgpdfs/fcpu28.pdf

http://www.britastro.org/dark-skies/crime.html

http://www.crimereduction.homeoffice.gov.uk/burglary/burglary45.htm

http://informedesign.umn.edu/Rs_detail.aspx?rsId=1548

http://www.astrolab-parc-national-mont-megantic.org/data/pollum/Lighting_and_crime.pdf

http://www.popcenter.org/Library/CrimePrevention/Volume%2010/index.htm

http://bjc.oxfordjournals.org/cgi/content/abstract/44/3/441

http://www.selene-ny.org/downloads/lightingandcrime.pdf

http://www.palgrave-journals.com/cpcs/journal/v5/n2/abs/8140143a.html
http://www.maltastro.org/lpag/

http://www.darksky.org/resources/links/crsesali http://amper.ped.muni.cz/light/crime/lp040_1h.html          (this particular study debunks many commonly cited references suggesting a significant lighting effect on crime deterrence. In fact, the major point here is that though the UK has made tremendous investments in lighting, crime is up 28 %.)


Cutoff Lighting

The purpose of cutoff lighting fixtures is to illuminate objects and surfaces below the lighting fixture while minimizing light pollution. Two forms of light pollution are light trespass (light entering areas that should not be illuminated, such as home or apartment windows) and sky glow (light entering the sky which reduces the visibility of celestial bodies). Cutoff lighting fixtures minimize light pollution by reducing or eliminating light leaving the fixture at angles greater than 90 degrees from nadir (straight down), while full cutoff lighting keeps all light emitted below the horizon. A cutoff fixture efficiently illuminates surfaces and objects below with minimal light waste and light pollution. Non-cutoff fixtures are less efficient in that they consume more energy for the desired illuminance level, and produce light pollution. A cutoff fixture located above the surfaces and objects to be illuminated will always produce more desired illumination then a non-cutoff fixture using the same amount of energy, or the same amount of illumination using less energy.

A very good illustration of cutoff lighting with different angles can be found at the British Astronomy Society page: http://www.britastro.org/dark-skies/misconceptions.html along with a discussion of other common misconceptions. This article describes the ideal full cutoff fixture as one that minimizes horizontal light but maintains a good spread of light of approximately 150 to 160 degrees. Further, they note that the main cause of light pollution is from light emitted at or just above the horizontal.

An International Dark-Sky Association publication on “Basic Lighting Laws and Some Notes on Pole Spacing Geometry” (http://data.nextrionet.com/site/idsa/is078.pdf) provides a brief summary of pole height and lighting distribution which also addresses issues of vertical illumination and uniformity:

“The mounting height of the lighting luminaire above the ground, the horizontal spacing of one pole to the next, and the cutoff angle of the luminaire are all important issues in outdoor lighting design, just as much as is the choice of the luminaire, the lamp type, and the wattage….At high cutoff angles, the X (the distance from the position directly beneath the light source and the point where the light hits the surface) and D (distance from the source to where the light hits the surface) dimensions really stretch out, and the D2 values show that there is little light left. There is no excuse for not having cutoff values be 80° to 82.5°. Any higher angles do not add anything to the effective light distribution, but they still do produce significant glare.

            In fact, cutoff angles in the range 75° to 80° appear to make the best sense. This still allows sufficient overlap of the beams from two adjacent fixtures. The key to designing a “good” lighting fixture is to get the maximum light output at an angle of say 65° to 70°, thus getting a good light throw out away from under the light fixture (avoiding a “hot spot” under the fixture), while at the same time getting a sharp cutoff at an angle of 75° to 80°.

            The result is then a nicely uniform distribution of light on the ground, out to a distance of at least six mounting heights from the pole, minimum glare, and no direct uplight. In addition, the designer must allow a good lighting distribution in an orthogonal direction (across the street, for example). It is possible, and such fixtures do exist. There is no excuse for not using them; they cost no more.”

 

Additional discussion on the advantages of cutoff lighting on glare can be found on another IDA publication: http://data.nextrionet.com/site/idsa/is123.pdf

 

There are different types of cutoff fixtures (see "Full Cutoff Lighting: The Benefits" by Douglas Paulin LC at http://www.iesna.org/PDF/Archives/2001_04.pdf, page 52) where he states “It is difficult to conceive of a luminaire being classified Full Cutoff if it has anything but a flat lens which is parallel to the ground.”  An excellent set of definitions are from the Lighting Research Center (http://www.lrc.rpi.edu/programs/NLPIP/lightinganswers/lightpollution/cutoffClassifications.asp) which states:

“The Illuminating Engineering Society of North America (IESNA) defines several outdoor luminaire cutoff classifications, each with different photometric criteria. For these classifications, two relevant zones are defined with respect to the nadir of a luminaire (the nadir is defined as the angle that points directly downward, or 0°, from the luminaire). One zone applies to angles at or above 80° above nadir, and the second zone covers all angles at or above 90° above nadir, or above the horizontal plane of the luminaire (see Figure 11). Light emitted in the 80° to 90° zone is more likely to contribute to glare, and light emitted above the horizontal is more likely to contribute to sky glow. The four IESNA classifications are defined as follows (IESNA 2000):

However these classifications can be quite misleading. There is a detailed technical explanation of the actual amount of light that is allowed to go skyward from any fixture that is not full cutoff at: http://www.lrc.rpi.edu/programs/NLPIP/lightinganswers/lightpollution/indicatorDirectUplight.asp. The gist of this article is that up to 16% of light in a cutoff fixture may be uplight which is undesirable and up to 31% for a semi-cutoff luminare.

What Other Communities are Doing

·         Ann Arbor to install LED street lights downtown (Posted by Tom Gantert | The Ann Arbor News October 17, 2007 08:00AM) - Info on Ann Arbor's downtown LED plans: http://www.mlive.com/news/annarbornews/index.ssf?/base/news-24/1192632347246110.xml&coll=2

Summary: Converting all its downtown lights will save the Ann Arbor $100,000 a year in energy costs and reduce greenhouse gas emissions by the equivalent of taking 400 cars off the road for a year. Claim to be the first US city to move all downtown lights to LED light bulbs.  Project will take 2 years at a cost of $630,000. Mayor says that eventually the entire city will have LED lights. The LED lights also provide better light quality for improved visibility and safety, according to LED City (www.ledcity.com), an organization of government and industry parties that is promoting their use.

Raleigh, N.C., and Toronto are two other cities that have installed LED lights in their downtown according to CREE (www.cree.com), the company that manufacturers semi conductors in LEDs but haven’t committed to doing their entire downtown.

The older street lights have a two-year life after which they all had to be replaced. The LEDs have a seven-year warranty and are expected to last as long as 10 years and don’t contain mercury.

According to reports, roughly 22 per cent of the US's total energy production goes to lighting. LED City initiative, the joint industry-government working group, was set up in February 2007 in Raleigh, North Carolina, to promote LED lighting as a way of reducing this figure.

According to the US Department for Energy, if LEDs were widely adopted, the amount of energy spent on lighting could probably be halved. Over the border in Canada, Toronto's officials estimate that replacing its street lights with LEDs will save it $6m a year in electricity costs, and cut CO2 emissions by 18,000 tons annually.

ALAN WARREN/ANN ARBOR NEWS: The LED street lights provide a whiter light compared to the existing incandescent ones. Note that these are retrofit lights taking advantage of the directionality of LED so as to minimize light pollution upwards:

large_LEDLIGHTS

·         Toronto's LED lights with photos: http://www.ledsmagazine.com/news/4/3/1

·         Raleigh's use of LEDs (plus new video): http://www.wral.com/news/local/story/1201312/

·         Calgary, Canada – a very early adopter planning to save millions:  http://content.calgary.ca/CCA/City+Hall/Business+Units/Roads/Street+Lights/Technical+FAQ.htm  and in particular:
http://content.calgary.ca/CCA/City+Hall/Business+Units/Roads/Street+Lights/EnviroSmart+Photo+Gallery+.htm

·         Torraca, Italy - From the Economist: http://www.economist.com/business/displaystory.cfm?story_id=10214726&CFID=27917664&CFTOKEN=95242352

“Low-energy illumination is lighting up the Dutch electronics giant. This weekend the Italian village of Torraca proclaims itself the world's first "LED city", unveiling new streetlights that emit a bright, white and ecologically green glow. The new lights use light-emitting diodes (LEDs)…”

See photos of Torraca's lights at http://www.cityledlighting.com/torraca/ . Note: These are not full cutoff or even shielded lights. We can do much better here, LEDs and full cutoff.

·         Montreal, Canada: http://www.protopage.com/johnsrichards#/LEDs has a demonstration of LED street lighting in Montreal using a patented control system which:

1.      Allows LEDs to perform longer than a nominal 50,000 hours.

2.      Automatically compensates for light lumen depreciation so designed lighting levels are maintained.

3.      The controls allow street lighting levels to change, so for example; during off-peak hours the lighting levels may be dimmed and more energy may be saved.

Street Lighting Ordinances and links

Missoula Montana outdoor lighting ordinance, effective Jan 1, 2008: http://www.ci.missoula.mt.us/lighting/

“The social and economic need to standardize lighting” discusses mesotropic lighting and some recent work with metal halide lights with a goal to minimizing light pollution and improving efficiency in a community in France (http://www.iec.ch/online_news/etech/arch_2007/etech_1207/focus.htm).

 

John S. Richards, +Associates writes:

You can find more links about street lighting at: http://del.icio.us/JohnSRichards/streetlighting
Also see links at: http://del.icio.us/JohnSRichards/CIE (see the CIE TC-58 links)
I am on this CIE Technical Committee. There is a draft standard for Mesopic lighting calculations. A lot of progress has been made since our last quadrennial meeting in Beijing. Soon it will become a CIE global reference standard. This will correct a 75 year error in lighting calculations.


Thoughts About Lighting From Gary Cziko

I think the issue can be broken down into four components:

1. Directing the light where it should go -- not into the sky, not trespassing into adjacent areas: So-called "full cut-off" lights will direct the light down to the street reducing glare and light pollution. I don't see why we should even consider any lights that are not full cut-off lights.

2.  Providing an appropriate intensity of light throughout the area to be illuminated: How bright do the lights need to be?  They should be bright enough to safely see pedestrians, but not bright enough to read a newspaper except in spot locations such as bus stops and ATM’s. Lighting levels should be uniform and conform to IESNA’s lighting levels based on activities, Zones E1 through E4 (IESNA RP-33-99).

3.  Providing light of good quality:  This has to with its color (temperature). Certain colors allow mesotropic vision, which is a combination of night (scotopic) and day (photopic) vision. Fewer lumens of the right color can appear brighter than more lumens of the wrong color.

4.  Producing the light efficiently: Using a light source such as LED may have higher initial cost but use about half the energy of high-pressure sodium lights and last much longer, about 60,000 (that is almost 14 years if burned 12 hours/day). LED also allows more control of the lighting.

Gary’s five E's for lighting:

Here's a simple scheme of five criteria, each starting with "e." Our outdoor lights should be:

  1. Efficient. Getting the most light per watt (lumens per watt).
  2. Effective. Putting all the light where we want it--down on the ground. Not sideways causing glare and light intrusion. Not up causing sky glow. The color of light produced also has an impact on effectiveness, with some colors allowing a combination of day of night vision.
  3. Economical. Total cost of purchase, installation, operation, maintenance, and bulb replacement. Fully shielded lights also put more light per watt on the ground allowing use of lower wattages per lumen.
  4. Ecological.  Effect on birds and insects. Minimizing greenhouse gas emissions. Reduce mercury contamination (LED lights do not contain mercury, unlike mercury-vapor and sodium-vapor lights).  Reducing sky glow.
  5. Esthetic. Should look nice.

Whether LED lights will be best to satisfy these criteria is open to research and discussion. And tastes vary concerning what is aesthetic. But I don't see how or why there should be any debate about our lights being efficient, effective, economical and ecological, as described above.


Comments From Annette Stumpf  

At a quick glimpse, I like the lights that Ann Arbor installed:  http://www.treehugger.com/files/2007/10/asquared_michig.php. They look like a contemporary old-fashioned style. But one person who commented on this blog didn't like them at all, and further down it says they don't have the cut-off optics.  I'm not sure about either comment. It would take a while to go through all the details and figure out what lights you want to select based on performance characteristics.

That is probably what should be established:  performance criteria/characteristics for the lights you want to install, and then someone can assess available light fixture design to identify the options.  Finally, you can pick the lights that best meet your performance criteria.

One of the things we talk about with respect to lighting design is the "color" or spectrum of the light.  Sunlight has a lot of red in it, and is considered a "warm" color.  For instance, warm white fluorescent bulbs are more popular in the north, and cool white are more popular in the south. Here's a chart showing the basic color temperature for typical lights:  http://www.ledwaves.com/pages.php?pageid=24.

You want to pick a light color that lets the eye distinguish colors.  For instance, I remember hearing that it was hard to figure out what color cars were at night when Low Pressure Sodium lights were used (because they are very yellow and don't give very good color rendition).

I don't know what colors are available with the LED’s so you'd have to ask the vendors what the color spectrum is.  How well can people see the neighborhood and car colors with their lights?  Here's an example spec sheet that shows the light distribution (in Lumens, measured on the ground), the cutoff angles (above 90 degrees) and the color spectrum: http://www.lumecon.com/docs/R20_11_8_2007.pdf and here’s the webpage with the details:  http://www.lumecon.com/led_street_lights.html

Another informative article:  http://www.patmullins.com/ledlightmyths.html
http://www.patmullins.com/index.html  (disclaimer, I don't know this person, who pays him, or how credible he is, but the info I saw on his website looks reasonable to me......  but who knows).


Contributors

Charlie Smyth (Editor, 5/13/08, rev3draft3), csmyth@sbcglobal.net
Gary Cziko, gcziko@gmail.com
Amy Ando, amyando@gmail.com
Annette Stumpf, als319@sbcglobal.net
Anthony Cherolis, acherolis@gmail.com
Bonnie Fortune, fortune2@uiuc.edu
Mike Lehman, rebelmike@earthlink.net
Matthew Childress, childrss@uiuc.edu
David Leake, DLeake@parkland.edu
Mike Lockwood, melockwo@uiuc.edu
Rob Kanter, rkanter@uiuc.edu
Robert Lozar, robertlozar@netzero.net
Samantha Myers, uias@uiuc.edu
Stuart Levy, slevy@ncsa.uiuc.edu