Saturday, January 4, 2014

In praise of sodium lighting

Our community center last night at the end of the street

Since 1970 the light source of choice in most cities has been sodium vapor, those yellowish streetlights you see glowing everywhere.

Sodiums are an efficient light source but many lighting engineers despise their color. According to one New York lighting designer "There is this negative subliminal response…the connotation is crime." Says another: "Yellow light muddies the colors of surrounding neighborhoods and makes people feel less secure because the colors around them are not true."

In fact there is very little actual research showing any of that. Most research says nothing about light color, only light quantity.

Regardless, it was only a matter time before a new lighting kid showed up on the block. In this case it was the LED - light emitting diode.

For example Seattle, like most North American cities, is converting to more cost efficient LEDs. They might be more efficient but they they produce a harsh, sharp image on everything.

A decade ago I was guest editor of a publication on lighting and CCTV. My thoughts then: If street lighting enhances architecture where pedestrians can appreciate the facades and details of downtown buildings, there may be problems lighting a downtown so bright it detracts from the aesthetics.

Whenever I see downtown LEDs they remind me I was probably right.

The photos in this blog demonstrate downtown sodium lighting. They show how well-placed sodiums provide adequate lighting and highlight the beautiful textures in downtown architecture.

High risk facilities like automated bank machines can be well lit with sodium
In none of these photos did sodium lighting detract from prevention or turn people off. There are no people in the photos because, at least in the photos I took, I had to wait for them to move aside in order to show the effect. Obviously, sodium lighting did not make them feel less secure. In fact, the opposite.

We know very little about the impact of color on night time behavior, especially crime. And since no one is apparently paying attention to the crime and social impact of LEDs, I hope we don't learn, too late, that brighter isn't always better.

4 Replies so far - Add your comment

Anonymous said...

It's not counter-intuitive for me. I've always preferred the yellow light to the white light. Myself… But I do think it is an aesthetic thing. Not sure either will have a serious impact on safety provided the lumens are sufficient.

Andrea C

GSaville said...

Thanks Andrea, I tend to agree about sodium. Not in all cases, but in the aesthetic ones. I am struck, however, by the feminist research I've heard about from Toronto years ago suggesting women were more fearful under sodiums. Therefore, so the theory goes, white halides (or LEDs) were preferable. That always seems bizarre to me..and I'm still looking for the actual data!

Anonymous said...

Excellent commentary on lighting (your blog spot continues to consistently be relevant and well written and I continue to link to it as important “must read” on my web

I disagree somewhat however on LPSV/HPSV as lighting sources.

Certainly, Metal Halide and LED can appear harsh if overused and yes, the key issue is consistency of lumen levels and uniformity of light. I do, however, feel that the issue of color discrimination should not be dismissed.

Back in the 90’s as Director of Risk Management for Valor security, we had on-going issues with smaller older malls who had not yet converted and were still using LPSV and in some cases even Mercury Vapor light sources.

Witnesses giving descriptions to our officers or to police after the fact would provide statements like:
“It was a blue car- or gray- or --- green – maybe black.”

And I challenge anyone to pull up even a good digital quality dvd of a vehicle sitting still (let alone in motion) under sodium lighting to give accurate color distinction to clothing or vehicle color after the fact. I am a big fan of aesthetics and of “dark skies” but feel a balance can and should be struck that affords the best of all worlds.

A recent case I had in Tucson Arizona was enlightening. They seem to have good ordinances that satisfy safety security and cpted dictates while allowing star gazing pleasure and reducing light bleed and harsh glare.

John D. Roberts

GSaville said...

John Roberts

Thanks very much JD for your compliments on the blog. It is a labour of love for an approach I think will change lives for the better.

Your blog is one I also read and enjoy and I encourage others to check it out.

You make an excellent point. I certainly bow to your exceptional experience in sodium and halide lighting. You are of course quite right about the impact of color rendition and the ability to identify color distinction, especially in high risk security situations.

My point is simply that the aesthetics of halides, and particularly unstudied LEDs, makes them harsh on night-time environments.

The photos I showed in the blog (and some I will show in a future blog on parking lots) show that sodiums can provide plenty of adequate light while contributing significantly to make an outdoor environment attractive and enticing.

That in turn can have the effect of encouraging night-time walkers and all sorts of legitimate uses by getting folks outside to enjoy their street. I suspect that is possible with LED lights, but honestly I have yet to see an application where it works as well.

I'd love to see some empirical research on lighting that delves into these more subtle issues. As I mentioned in the blog, lighting research on security and safety is pretty crass - more is better is the hypotheses. We need much better research to answer the questions we are discussing here. Till then, who really knows?

Thanks again for the important perspective.