I've seen the light

February 12, 2020

LED street light in winterYou may have noticed something different outside your front door. Little by little, block by block, the streetlights are changing.

The old high-pressure sodium streetlights produce a distinctive orange colour of illumination. The bulbs (which have to be removed, discarded, and replaced every three to five years) cast light in almost every direction. A device called a photocell controls each fixture, turning the lamp on when it gets dark enough in the evening, and off again in the early morning light. This keeps our streets and sidewalks well lit and, presumably, safer than if we didn’t have them.

This service to the community doesn’t come cheap. Each year the City was spending $1.5 million on electricity, and another $500,000 on maintenance.

The new fixtures use light-emitting diode (LED) technology. LEDs may feel like the latest thing, but they’ve been around a long time. First reported in scientific journals in 1927, they didn’t achieve commercial success until 1962. I’m old enough to remember receiving one of those first-generation wristwatches sporting an LED display. Now every smartwatch, smartphone, computer, and TV has them. Everything old is new again.

The harsh electric-blue colour of early LED street lights was off putting for many. These days the technology boasts more natural-looking colours. Confusingly, the technical way this is measured - Correlated Colour Temperature, expressed in degrees Kelvin - has a lower number for what we think of as warmer hues. Those nasty, early fixtures had colour temperatures as high as 7,000K; the fixtures appearing in Guelph are below 3,000K. This makes them friendlier to the human eye, professional and amateur astronomers, and some nocturnal animal and insect species.

Another nice feature of the new lights is their Colour Rendering Index. This measures how faithfully the lights show up colour on illuminated objects. The old ones are terrible. Before lugging my waste carts for curbside pickup, I would look out to see what colour bins my neighbours had put out, hoping to save myself the trouble of looking it up online (although now there’s an app for that). It was to no avail. Beneath the orange glow of the old streetlights, it was impossible to distinguish grey bins from blue.

Now, when I’m looking out on my street before garbage day, I can actually figure out which bins my neighbours have rolled out. As you can see in the photo above, grey looks grey. Blue also looks blue. Not a big deal at first blush, but think how it changes things if a child goes missing after dark. Or if a crime is committed, you witness it, and you want to identify the perpetrator. With the old lighting, a red jacket or red car both looked brown. The new lights solve this problem.

In a similar vein, the new lights also offer better visual acuity. Edges and bumps on surfaces - the ground, especially - are clearer. This is good for drivers, better for cyclists, and critical for pedestrians. If while strolling along the sidewalk you fail to notice that one slab has heaved and the next has not, you may suddenly find yourself splayed out on the cement. An embarrassing experience for the young, a potentially life-threatening one for the elderly. The new lights make such a mishap less likely.

My son likes that the new lights are very directional. The old streetlight used to shine right into his bedroom. The new one shines on the asphalt, on the sidewalks, and that’s about it. Since the conversion is only partially complete in our neighbourhood, you can see old and new nearly side-by-side, so the difference is particularly noticeable. The orange glow of the old ones is visible for blocks. However, unless you’re within five or six houses from a new fixture, you might not even know that it’s there. (See photo below.) This has implications for public health. Light pollution, or “losing the night”, is associated with all manner of ailments from depression to breast cancer. The new lights, which comply with the standards of the International Dark-Sky Association, will help keep unwanted light out of our bedrooms.

The new lights sport another feature unrelated to the LED story. Like the old fixtures, they have photocells. However, they are also networked together wirelessly with “adaptive controls”. If one of the old lights burned out, or kept shining at midday, the City depended on citizens to report them. (I know some folks deliberately avoided calling in, because they rather liked the darkness that came when a nearby streetlight failed.) Now, so-called burnouts and day burners can be spotted right away.

The other interesting thing about adaptive controls is that they can dim the lights automatically. The street lighting standard, RP-8, specifies how much light is needed based on traffic. However, 7PM traffic is heavier than 2AM, so less light is needed off hours. The City could choose to dim the lights late at night, saving power and further reducing the impact on the nighttime environment, while still meeting the standard.

LEDs use less electricity than high-pressure sodium lights right out of the gate. In addition, because of their better colour rendering, improved visual acuity, and directionality, less LED light is necessary to provide the same performance. Finally, the adaptive controls allow the fixtures to be dialed back when less light is needed. All this adds up to significant electricity savings - 50% or more. They also need a lot less maintenance. LED street lights typically have a ten-year warranty, but experience shows that we can expect a service life closer to 20. No bulbs to change means lower bills to keep the lights running. Less electricity and less maintenance adds up to saved taxpayer dollars.

Streetlights new and old

All this sounds very rosy. There have been hiccups - the project was approved back in July of 2017, and just got started late last year. After the trucks were rolling, it was discovered that a lot of the wiring needed to be replaced, so Council had to approve more cash for that. And I have to admit, the new lights are so small compared to the old ones, the post-top models in my neighbourhood seem a bit puny on top of the thick lamppost - a bit like the piddly forearms on an otherwise fearsome-looking T-Rex.

Finally, you could argue that although the project helps with light pollution, it doesn’t do much for carbon pollution. The lights are on at night, when electricity demand is low, rates are cheap, and electricity is carbon-free because the natural gas-fired plants aren’t running. However, if we reduce nighttime electricity consumption, it frees up capacity on the grid for one of the most significant emissions reduction opportunities there is - electric cars.

So kudos to the City for making this change. As we move forward on our journey to net zero carbon, we may have to make some sacrifices. But by and large, the changes we anticipate will make life better, not worse. LED street lighting is one example of the shape of things to come.

Alex Chapman