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Operation “Le Jour de la Nuit” (Day of Night), 5 questions put to Christian Buywid – expert on public lighting at SPIE

Beyond limited extinguishing of streetlights in our towns and cities, new technologies are now available to local authorities to combat light pollution

Cergy, October 4th, 2016As, on 8 October, the 8th annual Jour de la nuit – a national initiative to raise awareness of the presence and effects of light pollution (through switching off of streetlights, night-time walks, stargazing and nature rambles, etc.) – will take place, Christian Buywid, Business Development Director at SPIE Ile-de-France Nord-Ouest (Infra Transports Télécoms operating department) recaps the latest innovations in terms of public lighting that mean French citizens can feel perfectly safe on the streets at night… and enjoy the stars as well.

Here and there, we see certain public authorities announcing that their streetlighting will be switched off during certain periods of the night. Is this practice becoming widespread?

Christian Buywid: Indeed, certain municipalities are already switching off their streetlighting, generally for periods of a few hours (midnight to 5am, for example) when there is almost no one on the streets. This might be a partial switch-off, only including some roadways or areas. The practice is still very uncommon, though - especially in urban areas.

Residents want to have streetlighting, mainly so that they feel safe. In rural areas, the residents are more used to complete darkness. They are not overly bothered by the switching off of the streetlighting.

Is switching off streetlighting a viable solution?

Christian Buywid: Obviously, when we do something like that, we can immediately see savings in terms of energy and cost. For instance, switching the lights off from 11pm to 5am could represent a 20-30% saving on the energy bill. There is another aspect, though, which is often overlooked: the premature ageing of the installations. Switching off the lighting over a certain period of the night actually means that the streetlamps are switched on twice... and switched off twice as well. The result is that the ballasts have to generate overvoltage twice as many times. Hence, the installations age 10-15% more quickly than normal. Finally, switching off your public illumination is not necessarily the best solution. At the very least, the issue needs to be carefully examined.

In many large urban areas, obviously, it is not feasible to switch off the streetlighting, even occasionally. Are we doomed never to see the stars in Paris, Lyon, Marseilles, Toulouse, etc.?

Christian Buywid: In a great many towns and cities (great and small), we still see lamps which diffuse everywhere and nowhere a large portion of the light they give. By definition, except of course in the case of the lighting of monuments or specific buildings, this type of lighting is of no benefit at all to pedestrians, cyclists and drivers, and is obviously harmful to biodiversity. Therefore, what we need to do is to focus the streams of light onto the pavements and roadways. In time, then, if all the major cities change their public lighting within the next few years, I am confident that we could see the stars if we just go to slightly higher ground.

Seeing the stars is all very well… but what about the population?

Christian Buywid: A high proportion of the urban population is so used to “high-density” public lighting that they no longer realise that the quality of their sleep is terribly badly affected. However, that is the first and main harmful consequence of defective public lighting: we sleep badly because we are countering the natural need to be in the dark at that time of the day.  And the same is true for birds, insects, etc., whose life is knocked off kilter: they think it's noon…, when in actual fact, it's 3 in the morning.

Ensuring the feeling of safety and comfort for everyone, preserving biodiversity, eliminating light pollution, making savings… in the final analysis, are there not simply too many aspects to be taken into consideration?

Apparently so. However, there are new technologies available which mean all these requirements can be fulfilled… provided there is willingness and the necessary investment. As we mentioned before, it is absolutely crucial to direct all lighting downwards. This may seem obvious, but there are still far too many “ball” streetlights (which, incidentally, are now banned) in our cities, towns and villages. Today, we know how to “light right”, adapting to people’s way of life whilst also generating significant savings. Lampposts 10m high are becoming a thing of the past: 5m is ample. Conventional bulbs are also on their way out: LEDs provide better lighting with a 75% energy saving, and they also last longer. And finally, public lighting can adapt to people’s way of life: less intense lighting in the dead of night, but enough to make people feel safe; motion detectors which switch the lights on as a pedestrian, a cyclist, etc. goes by. Thus, we do have solutions available, although it will take some time to implement them on a large scale.


SPIE Ile-de-France Nord-Ouest

Christian Buywid
Business Develoment Director
Tel. : +33 (0)1 60 91 28 68
e-mail :