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1. What is the entire scope of the conversion program?

The City has converted 2,196 city-owned streetlights along City streets to LEDs and is in the process for converting 31 “cobrahead” lamps and floodlights in city parking lots. As a separate project, the City has replaced 11 parking lot fixtures with LED fixtures and replaced the light bulbs in 135 decorative post top fixtures with LEDs.

2. How will this conversion effect the city’s energy use and budget for streetlights?

The LED streetlight upgrade will result in a 75% reduction in energy use when compared to current technology and lower the city’s electric bill by about $180,000 per year. These savings, along with a $210,000 rebate from National Grid, means this project will pay for itself within five years. As a reference, the 185,000 kWh per year energy savings are enough to power 120 average Massachusetts homes.

3. What other benefits are there in an LED conversion?

LEDs last far longer than existing High Pressure Sodium (HPS) streetlights. The new LED fixtures are rated to maintain at least 70% of their light output for 100,000 hours, which is about 20 years.
The LED fixtures will reduce light pollution and lower the amount of trespass light shining onto yards and into houses.
? Unlike the majority of the city’s current streetlights, the LED lights will shine almost no light above 80 degrees up from vertical and zero light above 90 degrees up from vertical.
? The new LED streetlights will produce 58% less light then the current HPS streetlights. However, they will look as bright as the old fixtures because the light they produce is more useful to the human eye.
? While current streetlights shine light in a 360 degree circle around the light, the new LED fixtures will shine light predominately up and down the street, greatly reducing the amount of light trespass into yards and windows.
Because they use less energy, LEDs also help to reduce greenhouse gas emissions. Switching to LED streetlights will reduce the city’s greenhouse gas emissions by approximately 300 metric tons of CO2 per year.
Light from the LED streetlights make colors look brighter and more “true” to natural color. Trees look green instead of brown, a blue car looks blue instead of grey. Due to this improved color rendition things appear brighter and sharper under LEDs which is why police and other safety personnel prefer LEDs.

4. What is an LED?

It is a Light Emitting Diode.

5. What type of streetlights did the LED streetlights replace?

The vast majority of the historic roadway streetlights in Northampton were High Pressure Sodium (HPS) cobrahead fixtures and a few were Mercury-Vapor (MV) lamps.

6. What does color temperature mean?

Color temperature of lighting is measured in Kelvin (K) units. Lower temperatures are warmer and yellower; higher temperatures are cooler and bluer. Our existing high pressure sodium (HPS) streetlights have a color temperature of 2200K. LED streetlights have color temperatures ranging from 3000K or lower (warm white) to 6000K (day white). The LED streetlights that are being installed have a color temperature of 3000K, which is the warmest color LED lamp that the city can install and still receive a rebate from the electric utility.

7. Hasn't the American Medical Association (AMA) raised health concerns about LED streetlights?"

In June 2016, the American Medical Association (AMA) issued guidance for communities on selecting among LED lighting options to minimize potential harmful human and environmental effects. The neighborhood streetlights installed by the City of Northampton meet or exceed the AMA's recommendations.

8. Shouldn’t the new LED streetlights be shielded so that drivers cannot see the source of light?

No, the new lights, which have been certified by the International Dark Sky Association to be a fully-shielded, full-cutoff fixture, are designed to provide a smooth transition from the brightest area of light directly under a lamp to the dimmest area between lamps. Adding extra shielding to prevent light from shining up and down the street would result in sharp transitions from bright areas to dark areas along the road. This would inhibit drivers and pedestrians located under the streetlight from clearly seeing cars and people located in the darker areas of the road. The source of light in an LED streetlight is directed downward enough to avoid causing drivers from experiencing disability glare from the light.

9. Will new LED streetlights produce unwanted spill light?

No, the new lights reduce unwanted spill light into homes and properties as most of the light is directed up and down the street. However, if a homeowner reports that there is light coming directly into their home from the new LEDs, the homeowner can request that the city evaluate the light to see if it fits the criteria to have a shield installed on the streetlight to control the unwanted light.

10. How do I report an LED outage or request a house shield?

The Streetlight Modification Form can be found on http://northamptonma.gov/1736/Streetlight-Modification-Request. You will be able to either submit your request online, or download the form and mail it to the Northampton's Energy and Sustainability Officer. For more information, contact Chris Mason at 413-587-1055 or cmason@northamptonma.gov.
The city will evaluate all requests for shields to determine if the streetlight’s position in relation to the house will result in more than 0.009 foot-candles of illumination from the streetlight reaching the house. If the city determines that this may be possible, it will have a shield installed on that lamp so as to block the lamp’s illumination from the house. Depending on which shield will block light from reaching the house, the city will choose to install a house-side shield, a street-side shield or a cul-de-sac shield.

11. Does the City use LEDs for any other fixtures currently?

Yes. The parking lot lights in the Hampton Ave parking lot were updated to LED lights several years ago. Also, the new ornamental post-top fixtures in the new Pulaski Park are LED fixtures.

12. How did the City determine streetlight wattages and brightness levels?

In the 1990s, the City unified the city’s streetlights by street classification (arterial, connector, and residential). This project largely follows what was done then by replacing HPS streetlights with LED streetlights that have the same perceived level of brightness as the old lights. However, there are a few exceptions: lighting in downtown urban areas will receive LED streetlights of slightly lower perceived brightness than the old HPS lamps; lighting along residential streets that are used during rush hour as cut-through streets will receive the same wattage (and brightness) of streetlight as all other residential areas (these streets had brighter lamps previously); and the amount of brightness in the industrial park will be greatly reduced by using lower power and fewer streetlights.

13. Did the City consider a wireless control system that would allow dimming of the streetlights?

Yes but dimming controls are not included in the project. The current cost of wireless controls added 40% to the overall project cost. In addition, the National Grid streetlight tariff does not yet reflect savings from dimming so the City wouldn’t save additional money on utility bills from dimming. However the City is adding components to each fixture that will make the streetlights dimming control-ready so we can take advantage of the technology when the prices come down and the utility savings are guaranteed to show up on our electric bills. In the meantime, many of the streetlights will be installed at a dimmer, lower-power setting resulting in the city producing less greenhouse emissions even if we don’t realize cost savings on the electric bill by doing so.

14. Have the LED streetlights resulted in higher levels of blue light?

Possibly, but minimally at the most. It is more likely that the new LED lights have reduced the amount of blue light produced by the City’s streetlights. This is because, while the light from 3000K LED lamps contains a higher percentage of blue light than found in the light from HPS lamps, the LED fixtures will produce far less light (58% less light) than the HPS fixtures. Remember, the light from LED lamps is far more useful to the human eye, so less light is needed to provide visual clarity and the city is reducing perceived light levels in several parts of the city. The City calculates that the new lights are producing somewhere between 24% less blue light up to 6% more blue light than the lamps they replaced.

15. Is there a connection between LED streetlights and circadian sleep cycles?

The City of Cambridge posted a helpful article on streetlights and circadian sleep cycles for their LED streetlight conversion project. An Overview of Street Lights and Circadian Sleep Cycles by Dr. Steven Lockley, Harvard Medical School, Division of Sleep and Circadian Disorders provides helpful information. http://www.cambridgema.gov/electrical/steetlightsandcircadiansleepcycles

16. What other Massachusetts municipalities have converted streetlights to LED?

This is not a complete list as more cities are making the conversion every month:

Amherst, Chelsea, Natick, Weston, Arlington, Dartmouth, New Bedford, Westwood, Bedford, Fairhaven, Newton, Winchester, Boston, Fitchberg, Randolph, Winthrop, Brookline, Greenfield, Salem, Woburn, Cambridge, Hamilton, Sharon, Cape Cod (20 towns), Haverhill, Shirley, Chelmsford, Holyoke, Watertown