James Lowenthal: Criticizes city’s approach on LED streetlights

  • An example of the new LED streetlights in use on Williams Street in Northampton. GAZETTE FILE PHOTO

Published: 10/24/2016 8:17:38 PM

Mayor David Narkewicz argues in his Oct. 6 guest column that the city is adhering to recommendations of the American Medical Association and the International Dark-Sky Association in its plan to install over 2,000 new light-emitting diode (LED) streetlights. 

I respect the degree to which the mayor has studied the details of the issue, and I applaud the energy-saving motivation behind the plan. However, there remain several important errors in the city’s approach:

1. The selected lights have correlated color temperature of 3000K, which doesn’t "minimize blue light;" the new lights will have well over 50 percent more blue light than the current high-pressure sodium lights.  They do adhere to the AMA and IDA recommendations — but only just barely. 

Other cities in the US and Canada have chosen instead to use new "PC amber” LEDs, which have a much “warmer” 1800K color, and still others have put their LED plans on hold to wait for the technology and science to evolve, as they are very rapidly. 

Our bluer lights will have more glare, more light pollution, and more negative health effects on humans and wildlife.  Northampton deserves better.

2. It is true that the lights the city plans to install are “full cutoff,” as recommended by the IDA, with no light escaping above 90 degrees from the vertical. This is good.  And it’s true that they have a glare rating of 1 on a 0 to 5 scale when used at their brightest setting.  But they still have rating of 1 at their lowest setting.  Most importantly, that glare rating 1 allows as much glare as you’d get from a completely unshielded incandescent 700-watt light bulb.  Northampton should be aiming for glare rating 0.

3. The Leotek lights the city plans to install do not have any glare shielding.  The AMA clearly warns against direct view of LEDs, because they are so small and so bright that they cause painful and dangerous glare much more easily than the diffuse glow of the old sodium lamps.  Anyone can clearly see the LEDs in the city's test lights on Pleasant Street, Randolph Place and Williams Street day or night, even from hundreds of feet away.  This is why the lights are so painful to look at at night.

Proper glare shielding, such as recommended by both the IDA and the AMA, would help cut that glare.

4. The city’s plan to shield only 150 lights now and wait to see which other ones shine into people’s houses later completely misses the point that glare is not just about light trespass into houses. Glare is a significant hazard for drivers, pedestrians, and bicyclists — a much greater hazard than the dark-light pattern of illumination on the road that the lighting industry and the city have been fixated on as they resist installing glare shields.  Citizens are rightly concerned about glare in all directions from all the lights, not just the light trespass from a few lights into nearby houses.

The “house-side shields” the city plans to install on those few lights cuts the glare only front-to-back.  Instead, the city should test and, if they work, install “cul-de-sac” shields, which cut glare both front-to-back and side-to-side, i.e. up and down the street.

5. It’s great that the new lights will be configured to accept future dimming controls. But it’s a missed opportunity that the contract the city negotiated didn’t include the controls now, as many other cities have done for even less money.

James Lowenthal of Northampton is a professor of astronomy at Smith College.

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