Why white light is best for our town centres


White lighting is twice as good at letting you see the face of someone else as that from the yellow light from high pressure sodium lamps commonly used to light our streets, according to new research sponsored by the ESRC and published as part of Social Science week.

It can therefore allow the same facial recognition as conventional sodium lighting while cutting energy use by 40 - 45 per cent, says a study led by Professor Tadj Oreszczyn, of the Bartlett School of Graduate Studies, University College London.

Professor Oreszczyn said: "People have been putting in sodium light because they think it saves energy. But the truth is, you need more sodium light to be able to see other people's faces properly in pedestrian areas. And if you put in this extra light, you use more energy not less".

Researchers investigated the impact that improved lighting can have on people's sense of security and social and economic activity in Britain's town centres and shopping areas. But Professor Oreszczyn believes the implications of the research apply to all lighting for pedestrians.

The laboratory study of white light and facial recognition was used to compliment the research in which new lighting was installed in Sutton Coldfield town centre and the local urban area of Swinton. Interviews took place with more than 3,500 visitors to these sites before and after the relighting.

And virtual reality techniques were used for the first time in the lighting design process at focus groups with retailers, town centre managers, and young people known to the police. Issues raised at these sessions led to the laboratory investigation into the importance of the colour of light in people's ability to recognise faces - an important contributing factor in people's sense of personal security in town centres at night.

Professor Oreszczyn said: "Previous recommendations on street lighting for pedestrians required set lighting levels irrespective of the colour."

"This has resulted in the widespread use of high pressure sodium lamps, due to their greater energy efficiency and long life. But the information we have gathered suggests that this is a false economy."

"We found that you need about half as much white light as yellow to be able to recognise faces at a given distance, with an energy saving of somewhere around 40 to 45 per cent."

One of the major factors facing people using urban spaces is the fear of crime, and this is linked to their ability to recognise faces before somebody enters their 'personal space.' The study found that people aged over 45 need 30 per cent more light than those under that age in order to recognise faces to the same degree.

Professor Oreszczyn said: "This may in part explain why the fear of crime at night time is greater among the elderly. Our study has shown that normal standards of lighting, if applied using high pressure sodium lamps, will not provide the necessary level of lighting to alleviate fear."

These significant new findings are being passed on to lighting designers and researchers through industry journals, and incorporated in British Standard design guidance for road lighting. The result will be a significant change to UK urban lighting.

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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