Left: Thorn Beta 5 (35W) in Wrexham, May 2004. Middle - GEC Z9454 warming up. Right: M60 motorway near Manchester, U.K., August 2018, reproduced with permission from Callum Fraser.

Low-pressure sodium lamps (SOX or LPS lamps) are destinctive for shining with a golden yellow light, as shown in the photo on the left. They are also an energy source with very high energy efficiency. They have several applications but are most commonly used in streetlighting - in fact they have been used in streetlighting in the United Kingdom and in various places around the world since the 1930s. However, they can also be used in science laboratories, security lighting, or simply as a novel lighting source. Its yellow light is caused by the sodium that is used within the lamp. When the light switches on, it glows red, and slowly warms up to yellow over the course of a few minutes, as shown in the sequence of photos below.

Advantages

Although many areas of the UK still use SOX lighting on streets and other roads, it is now in decline, often a victim of misinformation about its merits and drawbacks. A SOX light in fact has many advantages:

1. As mentioned above, SOX lights are very efficient in their use of energy.
2. They are more effective in rain, fog and snow as the light does not become blurred by passing through raindrops etc.
3. High contrast recognition: Although the colour rendering of a low-pressure sodium lamp is poor, the contrast between light and dark is very good.
4. It has a relatively low operating temperature, meaning it can be used with cheaper components.
5. The light pollution it causes is easier for astronomers to filter out because the light is monochromatic.
6. It is good for tunnel lighting as the elongated lamps may be aligned end-to-end to produce a continuous line of light, eliminating any stroboscopic effect.
7. The SOX lamp can be operated on low-cost electrical control gear.
8. SOX lamps do not require a cooling-down time before they switch back on.
9. They are easier to service than other lamp types.
10. Yellow is a cheerful colour of light and can help to combat the winter blues.
11. It can be disposed of without concern for some of the toxic materials found in some types of lamp such as mercury.
12. The amber/yellow colour of SOX light is easy to distinguish from white car headlights or red tail lights. Therefore it is easier to distinguish between an approaching car and a static streetlight during night-time driving.
13. There is evidence that SOX lights are less likely to attract insects than other types of light.

How to buy

Resources

Finally, below are a few links to other websites ...
http://www.midlandcountiesstreetlighting.co.uk/WhatsNew.html (Claire Pendrous)
http://www.martynhicks.uk/personal/html/streetlamps/streetlamps.html (Martyn Hicks)
http://www.simoncornwell.com/lighting/ (Simon Cornwell)
http://eclairagepublic.eu/site/ (French-language site)

All content on this website © Matthew Eagles 2005-2024 unless otherwise specified. Last updated 28th October 2024.