1637Lighting for East Washington or anywhere
- Oct 1, 2002The following relates to the lighting in the East Washington PROJECT DETAILS page:"Lighting Issues" quotes David Keith, a fellow subscriber to lighting lists who's work on roadway lighting has been found to disregard headlights and the effects of glare on visibility. In the "General Information on Cutoff" page Holophane uses Keith's data in their descriptions. Selling refracting lenses for lights has been their business since the 1890s. This is a recent reply to David Keith, condensed some. I'll gladly forward the complete message or thread to anyone who asks: keedo@...From: <ctstarwchr@...>
Sent: Friday, September 27, 2002 1:47 PM
Subject: [DSLF] Re: Measurement of Glare?
> In a message dated 09/27/02 david.keith@... writes: > > If this refers to any of the IES-published papers or the associated work I have done, then it displays a disregard for facts.>>>> Hi David,After reviewing your research last year I was wondering if you might perk up on that one. Meant to playfully tease you out of stealth mode. Hope you are not too angry with me. ;-) Connecticut's Full Cutoff statute was also established then. It requires FCO lighting on all roads and prohibits an increase of roadway luminance when replacement lights are fitted. More FCO fixtures are being installed here every day in the existing pole locations. I was somewhat skeptical of this practice without increasing pole spacing or fixture heights in the beginning, but examples I witnessed in other states carried my faith to give it a chance.So far, we have been able to reduce the wattages (& corresponding lumen packages) in some locations by as much as 63% (400w HPS dropped to 150w HPS) with absolutely no loss of *perceived* uniformity nor any noticeable degradation of the overall *appearance* of lighting quality. In fact, to the eyes' perception, the lighting quality actually appears to have improved by a significant margin. On a subjective scale of 1-to-10, from what I have personally witnessed, I would place the previous 400w semi-cutoffs at a 3 with the 150w FCO replacements at a very strong 9. Others concur on the vast improvements to visual acuity as well.Granted, the light on the road under the fixtures is far lower when measured by a light meter, however, the eye cannot tell the difference in the field as it adapts in an appropriate manner to scotopic and mesopic responses as nature has always intended. I can only attribute this new lack of glare to the perception of vastly improved lighting quality for the entire surroundings. The IES type III luminaires also provide enough backspill to see clearly about 30 feet behind the poles, too.As many savvy eye-friendly designers will agree, one of the main shortcomings of the current lighting design criteria is that daylight lumens (photopic) are the order of the day in all known standards. But is it an appropriate metric to use outdoors at night? Many examples around the country and continued scientific research on human vision are beginning to indicate not.New data suggesting we don't need that much light is very intriguing. The ETAL principles of the IES may also help speed photon bombardment reduction. I've often wondered if the ancient original standards were made arbitrarily by picking numbers out of the air simply to support the products that were available at the time.The fact that the eye can operate more efficiently on a broader scale in much lower illuminance levels than previously believed may be one of the best benefits offered by FCO when it is *properly* installed. The only complaints come when an FCO is not adjusted properly in a level position and distributes glare one way, and also the other side of the spectrum, when people don't think the fixture is working because they cannot see any glare at the source. The latter is an education factor--if the grounds lit up the fixture is working, plain and simple.We have kept our ears to the tracks and nearly a year after these retrofits were installed I am not aware of a single nighttime accident that has occurred in any of the areas where FCO was installed. We hope that trend continues. Especially people over 40 report they can finally see MUCH better when driving in these areas after dark.You are indeed correct that the FCO fixture costs $3 more to purchase than its semi-cutoff counterpart, a fact that both the CT General Assembly and also the Department of Public Utility Control considered to be a negligible amount and NOT a cost that utility companies could pass on to their customers. The cost to install FCO has been $0 because fixtures get replaced when the old ones wear out. This progressive measure is reducing costs in both operating expenses and purchasing the hardware. It is providing wonderful benefits for the municipalities in the form of substantial annual cost savings in a country where the economy is stretched to the limits. The energy consumption (and operating expense) that depletes fossil fuels has dropped by a significant margin, which will also help reduce supplementary forms of pollution and landfill overloading with spent coal and coke ash along with particulate matter in the air we all breathe into our lungs.I am presently trying to build a library of nighttime photos with before and after examples. When I get a few assembled I will let you know if you are interested in seeing them. All things are equal with my Bozo Olympus don't-need-a-brain to use it camera because it cannot fudge images and only allows a one-second maximum exposure time.I admit this is not much to offer in the form of sound engineering data for the moment, but in time we should have some pretty significant data. We have over 200,000 streetlights to change over to FCO via attrition, which I estimate will take around 20 years to complete. The DOT is in favor of FCO after they gained experience and learned about the many benefits it offers first hand -- their favorite is better visual acuity leading to safer roads. In some broad intersections the pole heights have been increased for uniformity, but the spacing interval has not changed nor has the number of luminaires. CT-DOT enjoys getting more positive comments about the lighting rather than hearing nothing but complaints about glare.The negative impact of skyglow, clearly visible when clouds hang low in the atmosphere has been significantly reduced in all areas over the new FCO lighting when viewing these areas from a mile or more away. The the new bulbs and luminaires offer a worse case scenario in regard to the maximum upward reflected light.For whatever reason it all seems to work here in the real world David. I realize and fully understand that your research report indicates by all reasoning that it shouldn't. In all honesty I don't have an answer why (yet). I do owe you a debt of gratitude for your research because it raised my level of awareness to the importance of unit power density, which turns out it is one very powerful sales tool. My FCO designs for some projects have achieved unit power density levels of 0.025 watts per square foot while achieving enhanced uniformity criteria listed in the RP-20-98 with the new system paying for itself in savings over previous systems operation costs in a 10 year period, so I truly do not know what happened with the theories in your report. Did one of us miss something important? I never modified any of the photometry files and I cross-checked my figures six ways to Sunday and they all look good.Sometimes human aspects should be considered above and beyond mere costs and numbers in outdoor lighting design, and no number can be applied to that continuum that I am aware of. The eye is a very diverse and powerful perception organ that continuously adapts to its environment. It is like drawing the image of an amoeba -- the shape is never the same each time you look at it. :-)) Bum analogy maybe, but I haven't had a wink of sleep since yesterday at 6 AM. Too much to do not enough time to do it! Sorry if our numbers disagree David.Cheers,Cliff Haas
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