On Tuesday, 27 August 2019 17:25:45 UTC+1, Commander Kinsey wrote:
So why isn't red, yellow, etc as easy to see? If you wear a bright
red tshirt, you aren't as visible as wearing a hi-vis jacket. Does
it convert all the wavelengths into one or something?

Not all, but some. It's fluorescent:

The current standard that sets the requirements for high-visibility clothing is EN ISO 20471:2013, under the PPE Directive 89/686/EEC. This replaced the previous standard, EN 471:2003, in 2013. In addition to laying out requirements on the construction of the garments, CE marked and certified products must conform to strict requirements on the performance of the materials, their colour and the degree of reflection from the reflective strips.

Hi-vis jackets and trousers have no €œactive€� or light-emitting function, relying instead on an external light source for their luminescence.
- the fluorescent material: this achieves visibility during the brighter part of the day but also helps to increase visibility at night

https://www.healthandsafetyatwork.co...ble-difference

In a 2009 literature review, nine papers were found that compared the visibility of fluorescent and non-fluorescent colours. All but one of those nine trials found that fluorescent colours were more visible to drivers. Fluorescent clothing in red, yellow and orange €” colours that contrast significantly with the riding environment €” was found to be most effective1.

During the day, fluorescent clothing takes ultraviolet (UV) light from the sun €” light we cant see €” and converts it into light we can see. The result is an increase in the total amount of visible light thats reflected off the clothing, giving fluoro clothing a brighter appearance. This is particularly the case in low-light conditions, around dawn and dusk.

https://cyclingtips.com/2016/06/does...make-us-safer/

Bright, synthetic and, above all, cheap, the ubiquity of high-visibility clothing means that it surely symbolises the Britain of 2010s in the same way that miniskirts summed up the 1960s.

It was invented by an American, Bob Switzer, whose ambitions of becoming a doctor ended when he was injured in an industrial accident during the 1930s.. While recuperating, he developed a fluorescent paint before fashioning the first item of high-visibility clothing from his wife's wedding dress.

High-vis first came to the UK in 1964 when it was trialled by railway maintenance workers in Glasgow.

https://www.bbc.co.uk/news/magazine-14720101

Peter Rhodes, a lecturer in colour at Leeds University, said: €œThere is definitely an element of colour blindness. In safety you are trying to stand out. Conspicuity is the key element, not brightness per se. And if everyone wears hi-vis, people tend to ignore you.€�

The biggest market for it now is children. Yoko, a manufacturer and importer based in Birmingham, says it has made an estimated one million hi-vis vests for children in the last year alone. Many of these vests are bought by companies, such as Specsavers and Toyota, which print their logo on the back and give them to schools, who pass them on to pupils, who in turn become walking adverts for these companies. Clever.

https://www.telegraph.co.uk/news/hea...ke-lemons.html

Owain