How not to light a staircase

Staircases represent a tripping hazard, and it is therefore not unreasonable to illuminate them under certain circumstances. However, as I have shown in the past, poorly designed illumination is actually much worse than no illumination at all. A (literally) brilliant example of this comes from the "Lustgarten" park in Potsdam:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

These lights combine both the wrong direction (shining horizontally rather than downward) with being extremely bright, which makes them terribly glaring, and makes it harder, rather than easier, to safely ascend the staircase. (Right after I took this photo, I misjudged the position of the first step and stumbled slightly, even though I was trying to shield my eyes from the glare).

What could be done instead? One interesting application I have seen is LEDs installed on the underside of a handrail. Unfortunately, I don't have any photos of a really good execution of this. Here is an example of an attempt that didn't quite work out:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

It's better than the example above, but is still a problem, because it's still too bright near the lamps. What pedestrians need is accent illumination that helps them separate the stairs from the surroundings. When you have most of the scene lit with ~0.1 lux from skyglow and other distant light sources, and you then put 50 lux directly under the handrail, you've now created a 500:1 contrast. Your visual system doesn't deal well with that level of contrast, and it makes it harder to see.

For areas that are not brightly lit, moonlight provides a good benchmark. A typical full moon night is around 0.1-0.2 lux, so if you're illuminating a fairly light concrete, you really shouldn't need any more than that.

Update (October 20, 2021)

I found a great example, also in Potsdam. Check out the lights at the front steps of the Ernst von Bermann Clinikum (hospital):

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

The photo doesn't do it justice. It's a beautiful installation, there is absolutely no glare, it's not too bright, the color is warm, and in real life the area between the stairs is also sufficiently illuminated by light from the surroundings. I hope I get a chance to return to these two locations with a luxmeter and a DSLR camera sometime soon to do a more proper comparison.

Great streetlamps in a Spanish village

Last summer I spent a single night in the Spanish village of Sant Pau d'Ordal. My room had a balcony, and a colleague and I spent several hours in the evening sitting on the balcony, talking shop, and watching a distant thunderstorm. The experience was really enjoyable, thanks to the well directed lighting in the village. Here is the view of the street from the balcony:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

If the village lamps had directed light upwards, then the balcony would have been flooded with glaring light, and the experience would have been much less enjoyable. Beyond the full cutoff nature of the lamps, I was also impressed with the extent to which they kept the light on the street and sidewalk, and avoided lighting the trees. Here's the view from street level in daytime, notice the flat full cutoff design:

This work by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

Great job Sant Pau d'Ordal, and thanks for a wonderful experience!

Excellent LED streetlamps

This December I visited my family in the town of Wetaskiwin, Alberta, Canada. The first evening that I drove into town I immediately noticed that the city had switched from Sodium lamps to LED, and I was very pleasantly surprised to see that the LEDs they chose shine the light very carefully. To see what I mean, take a look at the photo below:

Good streetlamps are invisible by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

You almost can't see the streetlights at all, because they shine light on the street, rather than into your eyes. On most lit streets around the world, you can see the lamps from kilometers away, because they shine a portion of their light directly into drivers eyes. These photos from Wetaskiwin show how unnecessary that glare is.

That being said, the lamps aren't entirely glare free, particularly for pedestrians (see below). However, in terms of (white) LED streetlamps deployed in an urban setting, these are the best I have yet seen.

Close-up glare by Christopher Kyba is licensed under
a Creative Commons Attribution 4.0 International License.

When you have a good light distribution, then you can light the streets and sidewalks, and avoid shining light into peoples bedroom or living room windows. Take a look at the photo below. One house is lit with Christmas lights, but did you notice the one to the left? The street and sidewalk for that house are lit, but the facade of the house is not.

Orion over LEDs by Christopher Kyba is licensed under a Creative Commons Attribution 4.0 International License.

Camera photos don't accurately represent what our eyes really see (which is why I often show photos using two different exposures). I didn't do that (or HDR) in this case, because I hadn't planned on taking photos and wasn't dressed for the cold. But you can take my word on it: as a pedestrian, you have no problem to see the house on the left, the camera doesn't show it because the exposure was set to highlight the lit snow.

Thanks to Rod Mc Connell and Noel Smith, I was able to get some information about the lamps themselves. They are the "RoadFocus" series manufactured by Philips lighting.

The only negative side with the current lamps is that they are 4000 Kelvin, which produces considerably more skyglow than a lamp with a lower color temperature (warmer, less blue light). But I hear the city is planning on switching to 3000K in the future, and is also thinking about reducing the wattage so that the lights don't shine overly brightly.

So hats off to the city of Wetaskiwin for choosing driver friendly low-glare lights!

Here is a copy of the original photo, in case you'd prefer it without the text.

Good streetlamps are invisible by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

A tale of two lamps

This photo is taken from the bridge over the Warschauer Strasse S Bahn station in Berlin (daytime street view). Good lamps aren't visible from the side or above.

Lamp comparison by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Unfortunately most lamps aren't good lamps, as you can see in the original:

Warschauer Strasse railway at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

It's pretty likely that the brightly lit area under the "good" lamps is overlit, because it's so much brighter than the other lit areas. So actually these lamps aren't really ideal either. But it demonstrates the point that there is no need to waste energy and destroy the night by shining light in directions that aren't at all useful.

Look what happened when Circle K improved its canopy lighting

Mike Weasner recently took some photos of a change in lighting at a Circle K gas station near Arizona's Oracle State Park, which is designated an International Dark Sky Park by the IDA. By installing the lights within the canopy rather than below it, the gas station kept its pumps well lit while eliminating the glare of the old lamps. The new design also greatly reduces the artificial skyglow produced by the site, because light emitted towards the horizon is the most likely to be scattered back to Earth before it reaches space, and because Circle K chose a warm looking LED with 3000 K instead of an LED with a higher fraction of blue light.

Improved Circle K lighting by Mike Weasner is licensed under
a Creative Commons Attribution 4.0 International License.

Local businesses and Chambers of Commerce are usually very supportive of efforts to create dark sky parks, because they tend to bring in a lot of additional visitors into the area. As you can see from Mike's photos, being near a Dark Sky Place doesn't mean giving up artificial light, it just means using it more wisely.

Lighting in Sherbrooke, Quebéc

The Third International Conference on Artificial Light at Night just wrapped up today in Sherbrooke, Quebéc. Walking through the city this evening, I took a few photos of some street lights that caught my eye. Sherbrooke has made a major commitment to minimizing the city's effect on the nighttime environment, and one of the ways they do this is by replacing older lamps with newer fixtures that don't send light up into the environment. You can see this really well in the photo below, where the fixtures aren't visible from above, but by the reflection in the water you can see how bright they are:

Full cutoff lights reflecting from a river by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Of course, near a waterway the ideal light shines only on the path and not into the water... But I think it's a great photo for demonstrating how full cutoff lights work. In most cities, there would be two bright spots - one from the lamp and the second from the reflection.

The same lamps were on the bridge I was crossing over the river when I took the photo, and I was impressed that in addition to not producing any upward directed light, they also have very little glare. Compare the two photos below - which street would you rather drive on?

Low glare streetlamps by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Glaring streetlamps by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

In a few weeks, the Artificial Light at Night conference will start to fill up with pdfs and videos of the presentations. There will even be a video of me, talking about the Loss of the Night app!

Lighting strategies in England

A number of English councils are experimenting with replacing dusk-till-dawn lighting with a different lighting regime, either involving dimming of lamps, or else switching them off. The Campaign to Protect Rural England has done a survey of councils to try to understand how widespread this practice is, what the councils reasons are, and to learn more about what types of strategies are being used. They've produced a 32 page report summarizing their findings that you can download for free. They've also made the short slideshow below to present the main findings:

Lighting survey results from cpre

If you found that interesting, you may also be interested in a related report submitted to the Department for Environment, Food, and Rural Affairs: A review of local authority road lighting initiatives aimed at reducing costs, carbon emissions and light pollution.

Finally, my group recently published a paper discussing recommendations that we suggest policymakers should adopt in order to reduce energy consumption, and reducing light levels during periods of little activity was one of our recommendations. The paper is unfortunately not open access, but you can download an author's copy from my personal website, Redefining efficiency for outdoor lighting.

Lighting in Durham, NC

I'm in Durham, North Carolina for a meeting, and since I've got jet lag I was out at 3 in the morning to use the Loss of the Night app and take some photos of the street lights here for the view from your app series.

There seems to be a mix of streetlamps here with the lamps changing from one pole to the next. I annotated the photo below to show the difference in glare between poorly designed lamps and full cutoff lamps:
 

Streetlamps by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

If you zoom in, you'll see that you can just barely see the glow from the well designed lamps. They put all of their light where it's needed, and don't send it way down the block to distract drivers! The photo below was taken by Connie Walker, and shows the kinds of poorly shielded lamps that are typical in this part of town:

I saw a lot of examples of incredibly bad parking lot lighting, and this was the worst:

Dark shadows by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

The lamp is basically inside of a tree, so there is a huge area of the parking lot that's unlit. It's not a real streetlight, it's just a floodlight tipped at an angle, so that it sprays light everywhere - except on half of the parking lot! You can see that it shines directly into the house windows as well - and that someone is awake (a light is on). Maybe they have insomnia because of the glaring lamp shining in their bedroom?

Floodlit house by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

I really don't understand what's going on in the next two photos. There is a really bright and poorly directed floodlight, but I'm not sure if it's supposed to be lighting the parking lot or the building facade. In the first photo, you can see that it's a really glaring light that is particularly poorly situated: right before drivers will make a left turn through a pedestrian crosswalk:

Turning hazard by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

I often hear that lights are bright in the US because of fears of litigation. But couldn't a driver that hits a pedestrian blame it on the glaring floodlight and sue the business? The next photo shows how glaring the lamp is for pedestrians:

Glaring lamp by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

And finally the business itself. At first I assumed that this was supposed to be facade lighting, but after seeing more parking lots I think the facade lighting may be accidental:

Lit facade by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

Here is a gas station that should really be using recessed lighting. It would eliminate the glare, and leave a similar brightness at the pumps:

Poorly lit gas station by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

You can see the same kind of floodlight disaster on part of the parking lot of the station:

Floodlit parking lot by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

But right across the street is a WONDERFUL example of how parking lots should be lit! Just look at how little glare there is! The parking lot itself had extremely good visibility, and was very well lit. Of course, since the bank is closed at 3 am, it's unclear whether the lamps need to be on...

Well lit parking lot by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

Finally, here are the glaringly white lights of our hotel parking lot. The surface brightness was probably similar to the photo above, but it was much less comfortable to walk there because of the glare:

Parking lot with glaring lamps by Christopher Kyba is licensed under
a Creative Commons Attribution 4.0 International License.

In case anyone wants the original copy of the first image (e.g. to translate the text), here it is:

Streetlights by Christopher Kyba is licensed under a
Creative Commons Attribution 4.0 International License.

Great parking lot and terrible stair lighting

On a recent evening in Dresden, I noticed some great area lighting in a mall parking lot. As you can see below, the visibility in the parking lot is excellent.

In this closeup focused on the luminaires you can see that these types of lamps send almost no light directly up into the sky and are not at all glaring. Why isn't every parking lot in the world lit like this? Beats me...

Parking lot lighting (closeup) by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Of course, it's impossible to tell by eye how bright it is. It's possible that these lamps are putting out more light than is necessary. It's also possible that they should have a warmer color. Regardless of whether these lamps were perfect or not, it's clear that they are excellent compared to the typical parking lot!

While I was visiting Dresden, I also noticed another example of how additional light can make your vision worse:

Dangerous lighting 1 by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

This lamp is intended to help people see, but it's right next to a stairway that is completely unlit due to bad positioning of the lamp! You can see how invisible the stairway is in these two photos from roughly the same angle:

Dangerous lighting 2 by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

In this case, you would actually be better of if the lamp wasn't there, and you were just navigating by artificial skyglow or moonlight.

Finally, a little contest. Comparing the last two photos, can you spot another lighting problem? Answer in the comments.

The view from your app

Yesterday we saw some examples of bad street lighting from Spain. Today app user Andreas Hänel provides us with some good examples of decorative street lighting, from Puente la Reina, Spain. Until recently, Puente la Reina was overlit with lamps that produced a lot of glare, and sent much of their light into bedroom windows and into the sky. Now, you can see that the streets are well lit, but that the house facades are quite dark, and there is almost no glare from the decorative street lamps:

Good decorative street lighting, Puente la Reine by Andreas Hänel is licensed under a Creative Commons Attribution 3.0 Unported License.

In this photo from the Plaza Julián Mena, you can see an example of both poor and excellent decorative lighting:

Decorative street lighting in Plaza Julián Mena by Andreas Hänel is licensed under a Creative Commons Attribution 3.0 Unported License.

The lamp at top left wastes a large fraction of the light that it produces, by sending much of the light where it's not needed. The lamp at center right casts its light only downward, towards the ground. For comparison, here is the daytime view from Google street view. In Puente la Reina, before they changed the lighting many areas were extremely overlit. By directing the light better and using lower ground lighting levels, the town was able to cut its electricity consumption and energy bill drastically. The result is well lit streets, that are more attractive than they were before the lighting intervention.