You may have wondered: Has UV light ever been considered as a supplement to automotive lighting? The short answer to that: yes. For that we have to go back 30 years in time.
In the early 1990s, Volvo and Saab, among others, conceived the idea of using UV light in headlights. Of course not as a replacement for the halogen units, but as a supplement. After all, UV light has the property that it illuminates fluorescent substances or objects. When it comes into contact with it, the effect of UV is visible to the human eye. You can already feel it coming: the idea was that in combination with this it could be interesting for use in cars. In other words, UV could improve vision in dark conditions.
Of course you know the safety vests of road workers. These light up quite a bit if you just put light on them, that’s the whole idea behind 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. What if you also make road markings fluorescent? Then you can ensure that it is also a lot more visible when your car radiates UV light on it. That was the idea behind an experiment by Volvo, among others. That wanted to try out how much better the view of the road and various objects would become with UV lighting, as an extra to the standard lighting.
Promising
This turns out to be a rather obscure and largely forgotten experiment. We had to dig a lot to find something about it. The first information about the Volvo and Saab experiment was found in Techzle number 40 from 1990. It stated that the visibility of fluorescent objects in bad or dark weather conditions could be no less than 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 things would light up 150 meters away, if fluorescent.
After digging a little further, we hit a research report from the United States. This refers, among other things, to a Volvo 960 which, in addition to its halogen spotlights, also had UV lamps from Ultralux on board for an extensive experiment. Numerous experiments have been carried out with it in the US state of Virginia. For example, test subjects were put into unfamiliar situations with a car with and a car without UV lamps. Among other things, an unknown route had to be driven in the dark and objects or people were placed in front of the car at variable distances, sometimes with an oncoming vehicle with headlights on to make signaling it even more challenging. As it turned out, even though the subjects were left completely in the dark about the presence of UV lamps, the majority noticed significantly better visibility in the car using UV.
The detection of objects was measured. With UV light, a curve was discovered 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, one 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.
Rather not
All in all, it is certainly not a bad idea to use UV light as an extra on cars, you would say based on these results. However, it was already known at that time that problems would probably arise mainly because of the harmfulness. UV light is harmful to different degrees at different wavelengths. In the early 1990s it was stated in this study that there would be ‘no harmful consequences for public health’. This would have been shown, among other things, by research by a Swedish traffic institute. The UV radiation used had a wavelength of 320 to 380 nm, or UVA radiation. At the time, this was still seen as ‘safe’, but it later turned out that this UV radiation can also cause skin cancer, among other things.
Undoubtedly, that insight has suppressed the truly widespread use of UV light in headlamps. Yet there may also be something else involved. While these experiments were taking place, work was already being done on another type of lighting that offered more visibility mainly because of a simply more powerful beam: HID lamps (High Intensive Discharge). Popularly ultimately known as xenon lamps. They eventually took over the role of the obsolete halogen lamps. Later again, LED lighting became a thing of the past, making the poor visibility for which a solution was sought in the early 1990s a thing of the past.