DDOT will be Converting Streetlights to LED Lights Citywide

Here’s something that should be of interest to everyone. DDOT is beginning the process of converting our streetlights to LED lights citywide. I understand they are currently working in the Chevy Chase area. Thus far, I’ve only heard of some concern about light levels in one particular alley, but I know that DDOT is working with the residents there to find the appropriate lighting level. I’ll see if I can get more information from DDOT on when we might see this work in Park View.

Below is information about this conversion from one of the local listservs:

The District Department of Transportation (DDOT) will convert all the existing streetlights to LED lights over an 18 month period.   The purpose of this conversion is to improve safety in our streets and alleys; increase the longevity of the streetlights and save energy.

Community Involvement

DDOT has engaged with the community, DDOE, AOC, CFA, ANC Commissioners, US Naval Observatory and the Downtown BID, at the genesis of the project.  As DDOT implements the full LED conversion it will continue to engage the community to address residents’ concerns on LED lighting technology.

Please note: DDOT will revisit alley locations where installations have been completed to investigate any lighting issues. If challenges are identified, corrective actions will be taken and completed in 3-4 weeks contingent upon the weather and materials availability.

Energy Savings and Environmental Effects

LED is a proven and reliable source for street lighting applications. It reduces the energy consumption by 50%. It also requires little or no maintenance for at least 50,000 hours of use. This also entails reduction in CO2 emissions. Below is a typical power consumption comparison table of HID fixtures and the LED fixtures.

Application HID LED
Alley Lighting (cobra head) 70W HPS, 100W HPS, 150W HPS, 189W INC, 295W INC 50W or 75W.
Street lighting
     Cobra head 400W HPS 215W
     Cobra head 250W HPS 110W
     Teardrop 400W and 250W HPS 200W
     Washington Globe 400W, 175W MH, and 250W HPS 100W


Light Trespass

The selected LED fixtures were evaluated under this criterion by checking whether the light emitted in the 60-90 degree zone is at minimum value. The current high intensity discharge (HID) lighting system (High Pressure Sodium, Incandescent, and Mercury Vapor) and competing LED fixture products were used as baseline for comparison to determine whether the LED fixture is emitting less light in the 60-90 degree zone. The lesser the light emitted in this zone the better it is as lights emitted from the fixture are directed on the roadway and used efficiently. Unlike the conventional HID lighting which emits light 360 degrees, LED is directional and allows for greater optical control and efficiency. We evaluated the approved fixtures based on the actual sample installations and on independent laboratory test results which details the lights emitted in the 60-90 degree zone.  DDOT selected the LED fixtures available with the least amount of light levels in the 60-90 degree zone.

Although we strive to keep light trespass issues at minimum level, it is inevitable that we will encounter these kinds of problems due to workmanship during installations. This is more of a quality control issue which can be easily corrected by proper leveling of the fixture. The fixtures also come with shields to further minimize light trespass and will be installed if necessary.

Light Pollution

Today, the light pollution in the District is a major concern. DDOT has always been looking for product solutions that will significantly minimize this problem without compromising the Washington signature fixture. DDOT believes that with LED lighting and its approved fixtures, light pollution problem will be significantly reduced and in some cases completely eliminate the problem.

Again, light pollution is one of the criteria that DDOT considered in selecting the LED fixtures. To measure this requirement, manufacturers were required to submit the laboratory tests results outlined in the methodology for measuring the performance characteristics of a luminaire. DDOT evaluated the BUG (Backlight, Uplight, and Glare) rating of each fixture. At the time of evaluation, DDOT selected the fixtures available with the least amount of uplight.

Nevertheless, DDOT is taking every effort to make sure that light pollution is kept at negligible level and eventually make the city darksky compliant.

Blue Light

Currently, the International Darksky Association Fixture Seal of Approval requires luminaires to have a color temperature less than 4100K.  Having color temperatures at or below 4100K provides a more neutral color temperature without the harsh blue light of higher color temperatures such as 4500 to 6000K.

At the onset, DDOT’s approved LED alley light fixture has a color temperature of 5000K; the reason is that at the time of evaluation LED technology was at its infancy and the higher the color correlated temperature, the more efficient the fixture will be, which means high energy savings. DDOT recognized the minimum amount of blue light that are present at this color temperature, but two years ago this was the best available LED fixture and installed over 1300 lights citywide. However, with the advancement in LED technology, and in conjunction with MSSLC and International Darksky Community, DDOT has chosen to reduce the color temperature to more neutral color. DDOT is continuously seeking for improvement in the color temperature aspect as LED technology evolves.

With the entire available roadway lighting technology today, DDOT is convinced that LED lighting technology is the solution to these issues and will continuously work with the community to deliver the services they need.

Below are links to more information about the latest science of light at night by USDOE and MSSLC, the results of DDOT LED Study, and FHWA 2012 Lighting Hand Book.



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2 Comments on “DDOT will be Converting Streetlights to LED Lights Citywide”

  1. according to the Lighting Companies in dubai city-wide lighting upgrade will provide reliable and energy-efficient street

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