UV light is gratefully used to recognize counterfeit banknotes or to reveal traces of a crime.
Could it also give motorists a better view of the road?
Yes, Volvo thought.
In the early 1990s, Volvo and Saab, among others, already had the idea of using UV light in headlights.
Not as a replacement for the halogen lamps, but as a supplement.
After all, UV light has the property that it illuminates fluorescent substances or objects and can therefore improve vision in dark conditions.
Take the safety vests of road workers.
They light up quite a bit if you just put light on them, but they become even more visible under UV light because of their fluorescent property.
Even ordinary clothes can have that property, for example if the clothes have been washed with whiteners.
In that context, it also seems interesting to make road markings fluorescent.
Motorists then get a much better view of the road course or any other lines or markings, as soon as you shine on them with UV light.
Volvo found that thought interesting enough to start experimenting with it.
It became a rather obscure and largely forgotten experiment.
had to dig a lot to find anything about it at all.
The first information about the Volvo and Saab experiment was reported in
number 40 from 1990. It states that the visibility of fluorescent objects in bad or dark weather conditions can be as much as twice as good.
For example, the light from conventional lamps at the time would have been good for illuminating objects up to 75 meters away, but with UV light, even objects at 150 meters away would already light up, if fluorescent.
A Volvo 960 was fitted with (extra) UV headlights
also found a research report from the United States.
It was drawn up by researchers from the American highway authority, comparable to Rijkswaterstaat, and a research institute comparable to TNO.
This report refers, among other things, to a Volvo 960 which, in addition to its halogen headlamps, also had UV lamps from Ultralux on board for an extensive investigation.
Numerous experiments with the car have been carried out in the US state of Virginia.
For example, test subjects were brought into unfamiliar situations with a car with and a car without UV lamps.
Among other things, an unfamiliar route had to be driven in the dark and objects or people were placed in front of the car at different distances, sometimes even with an oncoming vehicle with headlights on to make signaling it even more challenging.
As it turned out, although the subjects were left completely in the dark about the presence of UV lamps, the majority experienced significantly better visibility in the car that used UV lamps.
"With UV light, a pedestrian crossing was detected 73 meters earlier"
The detection of objects was measured.
With UV light, a bend was detected only 8 meters earlier, but a pedestrian crossing no less than 73 meters earlier.
It was also investigated when objects were so clearly visible that the subjects could describe them.
At a bend this was the case with UV light 27 meters earlier than without, at an intersection even more than 57 meters earlier.
It also worked for pedestrians, who were detected 29 meters earlier (children) and 22 meters earlier (adults).
Cyclists even 157 meters earlier.
The latter is undoubtedly due to the fluorescent attributes on bicycles, such as reflectors.
Fluorescent road markings also turned out to be much more visible.
For example, motorists could see about two center lines further down the road and the uninterrupted lines on the right side of the road were visible almost 40 meters further than without UV lamps.
Ultimately, the UV light turned out to be harmful to health
All in all, it is not a bad idea to extend headlights with UV light, you would say based on these results.
Ultimately, however, the researchers could not ignore the fact that UV light can also be harmful to health.
And that is of course something you do not want if you want to improve road safety.
In the early 1990s, a study stated that there would be "no harmful effects on public health".
This is said to have become apparent from research by a Swedish traffic institute.
The UV radiation used had a wavelength of 320 to 380 nm (UV-a-radiation).
At the time, this was still seen as safe, but it later turned out that this degree of UV radiation can indeed cause skin cancer, among other things.
This undoubtedly made the researchers decide not to use UV light in cars anyway, although there may be something else involved.
While these experiments were taking place, Philips, among others, was already working on another lighting technology that offered more visibility mainly because of a simply more powerful beam: HID lamps (High Intensive Discharge).
These headlights eventually became mainly known as xenon lamps and many, especially more expensive cars have been equipped with them for years.
A completely different breakthrough followed even later: LED lighting.
This made the limited visibility caused by halogen lamps a thing of the past.