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County of Hawaii <br /> Dement ofPublic Woks - Traffic Division <br /> December 10, 2010 <br /> Wieffe044 <br /> To: COUNTY COUNCIL <br /> Thru: WARREN H. W. LEE, Director, Public Works <br /> From: RONALD L. THIEL, P. E., Chief, Traffic Division <br /> SUBJECT: OUTDOOR LIGHTING FOR ROADWAYS CONVERSION FROM LOW <br /> PRESSURE SODIUM (LPS) TO LIGHT EMITTING DIODES (LED) <br /> Over the past three years the Traffic Division has been researching the <br /> possible conversion of Low Pressure Sodium lights (LPS) to Light Emitting <br /> Diode lights (LED). The LED industry has introduced a very energy efficient <br /> product with projected savings up to 80% +/- in a cool light with a Kelvin <br /> temperature rating exceeding 5000K. This light, however, does not fall in <br /> the comfort zone of the human eye experience and is very damaging to the <br /> Astronomy observatory sky observations due to the high blue light content <br /> which is scattered much more easily than other light wavelengths and is seen <br /> as sky -glow by the Rayleigh scattering effect. <br /> Reasons for considering converting to LEDs are listed below: <br /> 1. Current energy costs for County Roadways in the Traffic Division annual <br /> budget is $1,200,000 and potential savings can be 50 to 60% amounting to <br /> an energy savings of $600,000 +. <br /> 2. Maintenance is greatly reduced because of the longer life expectancy of <br /> the light unit. <br /> 3. LPS lighting produces a harsh yellow light that competes with the yellow <br /> caution light of the traffic signals. <br /> 4. LPS lights have a color rendition of 5 on a scale of 100 where other <br /> available lighting products can achieve a 50 to 80. Blood appears black <br /> at an accident scene. <br /> 5. LPS s are not recommended by the lighting industry to be used in areas <br /> where safety is a concern because of the peripheral vision restriction <br /> especially at intersections where pedestrians and vehicles intermix. <br /> 6. LPS gives off a reflective glare, especially in rainy conditions, that <br /> impedes visual discernment of traffic lane markings. <br /> 7. There are programs that offer stimulus monies and rebates that may be <br /> available for the conversion <br /> 1 <br />